Next year there is a plan to send a space telescope to L2 with the main objective being to search for Earth-like planets around Sun-like stars in the habitable zone.
Like Kepler and TESS telescopes it will use the transit method to find new exoplanets, but unlike any mission before, it's going to look at the same spot in the sky for over a year. Super excited to see what data it brings back to us.
L2 as related to space telescopes was a new term to me, and turned out to be utterly fascinating. The Webb orbits the sun and periodically boosts velocity using Earth's gravity:
> The James Webb Space Telescope is not in orbit around the Earth, like the Hubble Space Telescope is – it actually orbits the Sun, 1.5 million kilometers (1 million miles) away from the Earth at what is called the second Lagrange point or L2.
Lagrange points are fascinating to me and I feel they are underrepresented in science fiction, compared to how the space age ahead of us may play out.
The events of human history on earth have revolved in great part around settling at or controlling strategically advantaged locations, for example any coastline, or a geographic bottleneck for trade and travel (think of Singapore and the Strait of Malacca).
A Lagrange point is the simplest space-based analog to this that I know of, if you want to put something in a fixed location relative to other bodies, the Lagrange points are places where you can do it with the highest fuel economy. Then when operating from that position you will have more energy available to do other things, granting you advantage over competitors who are not at the Lagrange point.
So whether it's science, research, trade, defense etc. there is a compelling reason to locate things at a Lagrange point, and it seems this is already happening as we have science satellites at L1 and L2 and I believe L3 has been talked about. The Lagrange points are not all created equal in terms of distance to their respective bodies, size, energy required to maintain a position etc. All two body systems have them, so for example the Earth and Moon have a set of Lagrange points that are significant to us.
The LPs are what a lot of our space politics and problems may eventually revolve around (quite literally!).
> events of human history on earth have revolved in great part around settling at or controlling strategically advantaged locations, for example any coastline, or a geographic bottleneck for trade and travel
Not only that, it's easier to send mass between Lagrange points than it is to send it to them from either of the orbital bodies.
Getting from Earth to L1 or L2, each 1.5mm km away, takes 15 km/s, escape + 12 km/s. (You have to fight both the Sun and the Earth's gravity.) Getting from L1 to L2 takes less than 100 m/s. (L1 to L3, L4 or L5 about 1 to 2 km/s.)
This confers strong defensive first-mover advantages; it's energy-wise easier to hold five than take one from the Earth. (Obviously, it's mass-wise easier from the Earth.)
Relays at L4 and L5 (also described in the linked Wikipedia) would be useful. If both are built it's reasonable for relay stations or satellites stay in contact continuously, if over different paths at different times of the day. The second relay station would also be useful if other objects naturally collected within the regions of stability disrupt communication.
Lagrange points are a key plot device in Iain M. Banks’s The Algebraist. I did figure out the location of the Dweller wormhole pretty quickly, thanks to thinking about how Lagrange points worked, but it is a great work of science fiction.
Regarding sci-fi; Joshua "Lagrange" Calvert did a fancy maneuver in Peter F. Hamilton's Reality Dysfunction involving a lagrange point that gave him that nickname.
I always wondered what kind of fun treasure might be hiding in the L4 and L5 points. And what kind of secret missions were already sent there by various countries to look for stuff. There could be whole precious metal asteroids sitting around!
Hi, thanks for answering the questions in this thread, it feels like something out of a sci-fi novel. Do you know of any similar projects that a software engineer could contribute to in their free time? Could be of much smaller scale of course.
To what extent (if any) will this program be impacted if all U.S. federal grant funding is permanently cut? Are there U.S. funded components/researchers involved?
As far as I know it won't be affected at all, the project is almost fully funded from the European Space Agency. And it will most likely be launched with the European Ariane rocket.
I wonder, is there any human endeavor other than space exploration (and maybe an occasional particle accelerator) that works like this? Sure, a big factor in the history of scientific progress is its structural resilience against localized political and economical kerfuffles, but that's more of an accident of how discovery and innovation are done - in small increments, achieved near-simultaneously by independent people or groups around the world (only one gets to take the credit, though). Meanwhile, it seems to me that space exploration needs to be organized into a competition to survive and thrive. To make things weirder, it's not about regular market competition - it's about staying in public consciousness, through continuously one-upping each other by Doing Something Impressive, which ends up attracting funding to all agencies each time (and conversely, when things get slow on the impressive achievements front, funding starts to dry out).
(We had one dry spell after Space Shuttles were retired, and IMHO this one could've been fatal to the entire field. Thank $deity for NASA's funding of commercial launch services, and SpaceX surviving 2008 and taking advantage of it to get the Falcon 9 to work and effectively re-light the public interest again.)
I imagine this is a transitional period; we're past the times of Cold War - times when everyone poured ~infinite money into weapons programs and space exploration got to leech some of it off - and we're not yet seeing the bootstrapping of cislunar economy on the horizon. I wonder if there's a more sustainable way of getting through to the other end, because relying on public interest feels rather risky. And, again, I can't think of any other field that is in this weird position.
Yes. In the past long-range sea voyages worked exactly in the same way.
They were seen as little more than expensive intellectual curiosities and eccentricities. In fact even once we discovered the New World had Columbus not come back and lied his arse off about riches that existed there only by coincidence (as he'd seen nothing of what he claimed), it's entirely possible that would have been the last journey to the New World for decades if not centuries. And over those decades you'd probably have had more and more of the population believing we never even landed on a New World to begin with.
And it'll be the same in the future. Eventually humanity will become a multiplanetary species and more value will be generated off Earth than on it. And I think we're probably not that far away from such point, but we live at a time when we will happily dump trillions of dollars to fund pointless chaos halfway around the world (that invariably just makes the world less safe for everybody), yet every penny that could take us closer to these species defining events is scrutinized like we're down to our last pennies.
And again - this isn't new. It's been the case for centuries and probably will be the case for the foreseeable future of humanity. It's easy to explain with a tautology - positions of power are held by those attracted to power, and those attracted to power are attracted to power. Once the New World became a means to power, that's when the 'trillions' started pouring in. The same will happen with space.
Yeah I was really looking forward to that alt history where the Aztec Empire reached technological parity with the rest of the world. All hail Huitzilopochtli!
Technology wasn't the primary cause in the genocide of the Native Americans. The initial factor was the introduction of plagues to the Americas from the numerous intraspecies transmission that occurred in the old world as a result of the millennia of large animal domestication alongside high population density that had no analog in the new world (since there weren't the same variety of large domesticate-able fauna, apart form like alpacas or something). This is also why there was no American plague that spread in the other direction.
Western Europe was certainly not so far ahead technologically relative to the rest of the world as people so frequently give them credit for. Not until they had free reign over a new continent and purchased slaves to generate free money (*) and eventually total dominance with the advent of the industrial revolution.
(*) This also led to an arms race between rival empires and kingdoms in Africa and the stagnation of local craft and the eventual the economic collapse and political fragmentation of the wealthy empires that existed throughout antiquity and the middle ages - that have since been written out of history books. When the industrial revolution began spinning up out of the ashes and rubble of Christendom post-reformation, many other regions like the Middle East (for example the palace intrigue and power struggles within the Ottoman dynasties) and China (With the collapse of the Ming and ascendancy of the great Qing from the North) were similarly in crises - in part from indirect economic interaction with the growing powers in the west. It was then the nascent imperial powers found the world ripe for their exploitation and eventual hegemony.
I'm happy to. But then, like most people, I'm impatient, so I'll draw a second plan that ensures I get to see at least some of the cool stuff before I die, and then I'll get annoyed when this plan isn't followed.
Galactic timescales are large. Human lifespans are tiny.
What's the typical time scale for a transit?
Also, why use transits instead of the Doppler method? Has this patch of sky been selected based on previous Doppler method star studies?
Thanks!
Generally measured in hours, or minutes. For example, if we were observing our system with perfect alignment, Earth's transit would be about 12 hours, Jupiter's transit around 29 hours.
> Also, why use transits instead of the Doppler method?
Quantity. PLATO can observe a sizeable portion of the sky at once, 100k+ of stars. With Doppler method the quantities are smaller + afaik there is a trade-off between number of stars being observed and the velocity we can measure. So to find Earth-like planets around Sun-like stars, we would likely have to go one or a few stars at a time.
> Has this patch of sky been selected based on previous Doppler method star studies?
I am not actively involved anymore. So I am not sure if they have already picked what part of the sky they PLATO is going to be observing. The previous Doppler method (aka as radial-velocity or rv method) star studies play a role, not only because if there's one planet, there might be more, but also because rv gave information about the star. However, keep in mind that this is to find new exoplanets, less to find out more data about existing ones. Rv will definitely be used along side PLATO, to confirm and gather more information about exoplanets that PLATO finds.
> Earth's transit would be about 12 hours, Jupiter's transit around 29 hours
…per year, for Earth; per ~12 years for Jupiter is I think what the GP was asking.
This is extremely dependent on the radii of the inner and outer limits of the the habitable zone for any given star, though, as well as the star’s mass.
Radial velocity surveys require so damn much light, and such a complex precision spectrometer that they're only used on the very largest 8m-10m class telescopes on the ground, shooting in near infrared through the most advanced adaptive optics (or even interferometric modes) in great weather, pointed at a single target for a long period of time (this is a big deal), with a focus on super-Jupiter to Jupiter class objects in tight orbits.
The next generation of 30m class telescopes will be an order of magnitude more capable for the RV method, but even then you're not really going to be able to get fast locks on Earth analogs.
The RV method is vastly superior for detecting the planets we really care about - high confidence nearby Earth analogs. The odds of a transit being in the right plane for us to observe are tiny. But if we want to run a survey like that like it really matters (let's say a Solar system catastrophe hits a thousand years from now and humanity wants interstellar diaspora), we'll be studying the nearest thousand stars with the RV method using significant numbers of 100 meter class telescopes, or perhaps big space based interferometers produced in mass quantities, for decades.
What transit studies like Kepler do is study a small patch of crowded sky (most of the stars being very distant) with the sensitivity for very rare in-plane Earth analogs, in order to get a representative sample. When I was born we couldn't say with any confidence that planets around other stars existed, post Kepler we know that they're common. We can perform these surveys even with the shoestring budgets current governments afford astronomy because even if the odds of successfully detecting a planet that does orbit a distant star are very low, we can watch a million stars at a time.
You can find much less massive planets with the transit method.
The Doppler method relies on the planet pulling on the star to change the star's line-of-sight velocity periodically. Because planets are much less massive than stars, the star doesn't move much. You can only find massive or close-in planets with this method.
The transit method is much more sensitive to small planets like the Earth. It's true that the smaller the planet, the less of the star's light it blocks, so it's still easier to detect large planets than small planets using the transit method. However, it's much easier to detect small changes in a star's apparent brightness than it is to detect small shifts in the star's velocity.
There are a few different viable methods of detecting planets. Each has its strengths and weaknesses, and astronomers use all of them.
Very cool. Got a silly sci-fi question for you. IIUC, with current technology it would take on the order of tens of thousands of years for a vessel to physically travel to the closest known Earth-like planet (correct me if I'm wrong).
So any thoughts on what kinds of hypothetical breakthroughs would be needed to make the trip doable in (say) less than a human lifetime?
A different stab at this is to ask what it would take to build a telescope that could image some of these Earth-like planets, a project that turns out to be easier (in a very loose sense of that word) than sending cameras there.
The idea is you send a camera very, very far out in the Solar System (hundreds of AU) and then use the Sun's gravity well as your lens. Neat stuff and, unlike the interstellar probes, potentially doable in our lifetime.
Normally, diffraction and the effective aperture are what limit optical resolution. How does that work with gravitational lensing? Does the effective aperture become the diameter of the sun?
I'm too ignorant to answer that, but the technical paper here [https://arxiv.org/pdf/2002.11871] goes into a wealth of detail, and includes an image of Earth as it would appear to such a telescope (before and after post-processing) from 30 parsecs away. The optical properties of the solar gravitational lens are pretty astonishing.
Self replicating automata as described by Von Neumann able to repair and duplicate themselves, and other things like electronic components. ICs keep getting faster (so far) but use smaller and smaller features of silicon and could wear out from metal migration and all components will be under much more cosmic radiation than on earth. This makes a large shield of heavy material on front of vehicle to minimize this effect but that increases the energy/fuel needed. The space shuttle only took maybe week long trips but it had four computers for flight control , three extra in case of failure in different parts of the shuttle along with IIRC a separate backup backup computer in for use as last resort.
* Research faster interstellar travel, especially using something like a Buzzard engine to utilize interstellar hydrogen as resection mass. Required nuclear fusion power plants / engines and ridiculously strong magnetic fields; both seem attainable.
* Slow down human body metabolism and allow humans to stay asleep at near-freezing temperatures for a long time. If bears and chipmunks can do it, chances are humans could learn it, too.
* Invent sets of machines that can reliably self-replicate, given most basic inputs like minerals, water, and sunlight. Advanced semiconductors are going to be the tricky part.
* Study psychology, sociology, history, game theory, etc, so that the early society that will form on the new planet, isolated from Earth, would avoid at least some of the pitfalls that plagued human history on its home planet.
>Slow down human body metabolism and allow humans to stay asleep at near-freezing temperatures for a long time. If bears and chipmunks can do it, chances are humans could learn it, too.
The thing is - our current bodies can't live in space for long. So either we will have to build new bodies for us somehow or build a ship that can have gravity inside and protection from space outside (and we are talking about very heavy protection here)
In any other case there is no point in slowing down metabolism or whatever. You will die rather soon.
Also, it won't work unless scaled up to the sort of thing only a Kardashev type II could do — 4000 km diameter — and at that level you've got other options that mean they probably won't:
Time dilation means that the closer you get to the speed of light the less time you experience passing. So even a 12000 year long journey as seen from earth, if moving fast enough, could feel to the travelers like a much shorter amount of time.
Yes, but practically with todays technology there is no feasible way of getting to a speed where time dilation matters over that distance, we run out of fuel so we need some external power source like a laser or solar wind that have other issues, iirc one only gets to 2x time dilation at 0.9 c. That’s a lot of acceleration.
We need to think about where we want the knowledge and what knows it. We could use humanoid AIs. We could hatch humans "just in time". Run them in a sim to 18 then release them on their mission. Ethics would need to accept this. Maybe we would be happy slowly expanding across the universe and an decendant talking to 'the aliens'.
I am not totally serious. But you wanna meet aliens? Gotta do something a bit radical.
If you haven't, you should read Accelerando, it's a collection of short stories IIRC that were put into a novel by the author. I didn't want to start with that, but that is in there. :)
If I may suggest another read: Perfect Imperfection by Polish author Jacek Dukaj. It's definitely weirder, than Accelerando, as the book drops you straight into the last parts of evolution curve, but definitely worth reading if you have liked Accelerando.
The story is super weird, but what I found out is that piecing together a picture of a far-future society from this story was very exciting.
The transit method requires observing a dip in the brightness of a star. Actually - three dips. The first dip indicates - but does not prove - the existence of a planet transiting in front of the star. The change in intensity, rate of change of intensity, and duration of the dip all give us information.
The second dip, if roughly identical to the first dip in parameters, gives us the orbital period of the star. So now we wait a second period in order to observe the expected... Third dip, which confirms the planet if it occurs with the same parameters at the expected time.
Though I think that such observations would require at least two years, and up to possibly four years, for stars with orbits of periods similar to our own. I don't believe that a single year is long enough.
> Though I think that such observations would require at least two years
It is at least two years at least if I'm understanding this⁰ correctly:
Observational concept
Ultra-high precision, long (at least two years), uninterrupted photometric monitoring in the
visible band of very large samples of bright (V ≤11-13) stars.
I should have been more clear in my original post. AFAIK there are two options on the table - looking at two fields, both 2 years OR looking at one field for 3 years and then doing "step and stare" for the rest of the mission. Step and stare being that they "step" into a new field, "stare" at it for some time, and repeat.
> Is it to get a more exhaustive survey single star or can full of stars?
PLATO will look at 100k+ stars at once. And for most we will be unlucky to see a transit between PLATO and the star. Geometrically it won't align - imagine the star systems being in different angles from us. To bring an analogue - Take a pack of cards and throw them in the air, and take a quick picture while they are sitll in the air - how many cards will be facing the camera exactly with their edge. For us to spot a transit, the planet has to pass between us and the star. If the orbital plane is not parallel to us, we will miss the transit. So that's one of the reasons why it helps to look at bunch of stars with transit method. We expect that about 1% of the orbital planes will be aligned so that we can get meaningful data.
> Or does that help it find smaller/further/different planets?
Imagine you are trying to find Earth from another solar system. The longer you look at our Sun the higher the likelihood that Earth will pass between you and the Sun. And once you get lucky, and the Earth transits between you and the Sun, the brightness of the Sun only dips about 0.01%, so that means that in order to find small planets we have to have sensitive instruments and little noise, so that the dip in brightness can be measured. Furthermore, as the planet passes the transit and continues on its orbit, the perceived brightness of the star will increase, due to the planet reflecting some extra light. Measuring that can gives us some rudimentary information about the atmosphere - e.g. if a small planet reflects a lot of light back, maybe it's covered in clouds or snow.
> And how do they pick where to point at?
There's a whole complicated process to find consensus on where to point. Basically they look at spots that have lots of stars, and they look what type of stars they are. Here the objective is to find planets around Sun-like stars, so they would prioritize fields that have more Sun-like stars.
> Is there a way of guessing the likelihood of finding a planet?
It seems that some stars are more likely to have planets than others.
Since I have your attention - I figure this is still the best condensed ELI5 explainer of the history and methods used in search for exoplanets, and I keep sending this to anyone remotely interested in the topic:
(I also consider it to be the only true, original, canonical rendition of the Alladin song.)
It gets into the transit method around halfway through (at 3:43), and makes it glaringly obvious why this is the way to go, over tracking Doppler shifts. Still, this video is almost 8 years old (and neatly coincided with discovery of additional planets around TRAPPIST-1) - I wonder if there are new methods at play that are not covered here, and of course if the middle part still corresponds to how things are done?
You said:
> We expect that about 1% of the orbital planes will be aligned so that we
> can get meaningful data
Somewhere below, someone used the figure of 0.01%. I assume they were mistaken, and your 1% number is about right for some "average" star sizes and orbits.
At any rate, that figure depends on the size of the star, and the distance from the star that the planet orbits--the further away, the smaller the chance that their orbital plane would be aligned with our solar system. For a Sun-class star, and a planet inside the habitable zone, what is the %? Am I correct in thinking it would be approximately 0.5/180, where 0.5 degrees is the apparent size of our Sun in the sky, and 180 degrees is of course half a circle (since it doesn't matter whether we're on one side or the opposite side of their star, hence 360/2). Which works out to about 0.14%, right?
How does the 0.01% look in comparison to the natural variability of star brightness, due to cycles, spots etc? Would that be a concern in terms of false positives? And also, given the specific line-up needed for us to see the pass, how likely it is for us to be able to observe the same planet in front of the star in the following years?
Stars do change their brightness in various other ways, but the light curve of planetary transit has a very characteristic shape. It causes the brightness to dim by a small but constant amount, with a (comparatively) very short and sharp start and end. A transit causes this pattern to occur at precisely regular intervals, and I don't think we know of any phenomena related to a star itself that would imitate the same effect.
Stars' relative positions generally don't change fast enough for the angle from which we observe a transit to change significantly. A transit of HD 20794 d is visible anywhere within a roughly 0.7-degree wide band. But our angular rate of motion with respect to the star HD 20794 is the same as its rate of motion in our sky, about 0.001 degrees per year. So the transit will most likely continue to be observable for decades or centuries to come, depending on exactly how the planet's orbit is aligned.
Would it be feasible to place telescopes at other orbital inclinations with respect to the sun in order to spot transits in stars that aren't within Earth's orbital plane ?
The orbital inclination relative to our sun doesn't really have anything to do with it. In fact, stars that are aligned with Earth's orbit are harder to observe, because they go behind the sun once a year.
Detecting an extrasolar planetary transit requires us to be aligned with the planet's orbit around its star. And since those stars are so far away, you would have to travel an immense distance away from our solar system to appreciably change the relative angle.
HD 20794 is about 20 light-years away from us, so changing our observation angle relative to it by 1 degree would require traveling about 0.35 lightyears. Our fastest-ever interstellar probe, Voyager 1, would take 5000 years to travel that distance.
Thanks for the clarification. You are absolutely right, in my post above I accidentally used the word "parallel" that caused the confusion. It wouldn't even be practically possible to use PLATO to observe them.
Probably not the best choice of words from me there. However, there is a positive correlation between a star's metallicity and the number of planets a star has.
Your words are fine from my point of view,
I am just tickled at the though of how hard it is to prove a star has no planets.
Even with all stars having planets, it is worthwhile to carefully choose
the field to maximize the chance of detection. Best would be if planetary disks aligned themselves in any predictable manner, but not much hope there.
Light collection. You want to observe one point for a really long time so you get a really good understanding of where the light is coming from, the properties of that light, and its behavioural patterns.
A lot of the detection is statistics around signals, so the better (read more thorough and coherent) your data (observations of changes in light), the more confidence you can have in your conclusions around what's causing the changes (planets with different atmospheres, different positions, different sizes and compositions etc...).
Figuring out the optimal placement of CCDs on Plato's 24(+2) cameras. Due to the way CCDs are fabricated, their properties vary a bit, they are not identical. For example, they can vary how much light they can hold before they become saturated. Given the high cost of fabricating these CCDs, and the fact that for each camera 4 CCDs are used, and all these 4 have to share front-end electronics, it was prudent to optimize their grouping to we maximise the dynamic range we get. More dynamic range means that we can tell more about the planets we find with higher confidence.
Yes. In telescopes they use high-end CCDs with really big pixels for better light sensitivity and zero dead pixels.
This is a picture of the CCD array for the Gaia space observatory that used parallax to measure precise distances and slightly less precise angular velocities of billions of objects
Good question.
No, these will essentially be black-white "photos". The amount of light is measured. The reason for so many CCDs is so that the field of view would be as large as possible. A larger field of view enables to look at more stars at once. Given that we will be locked into looking at one spot for a whole year, it ups our chances of spotting something cool if we maximise the number of stars we are looking at.
However they won't be photos of planets really. It will be countless photos of the same stars over and over again, it's just that sometimes they will be slightly less bright than other times. Directly imaging exoplanets is incredibly difficult, but humans have managed it: https://en.wikipedia.org/wiki/List_of_directly_imaged_exopla...
Do they move the telescope over the year to account for movement? How is that calculated? Does this change with being closer to planets and their gravitational pull?
Yes, it's something that's referred to as pointing stability. The telescope will have star trackers to precisely know it's relative position - basically you make sure that you see the correct stars from where it is placed on the spacecraft. It will use reaction wheels to make tiny correction's to its position. Imagine you are in a computer chair and trying to spin yourself without feet or hands touching anything, just by twisting your body. Reaction wheels work on the same principle. As Earth completes a year around the Sun, the gravitational pull from other solar system bodies is very minor on PLATO. That said, keeping a spacecraft in L2 is not easy - there is nothing to "orbit".
The orbital corrections are minimized at L2, because of the relative distance of the moon and other planets vs size. But that is what is accounted for in the corrections.
How far away PLATO will be from the James Webb Space Telescope? How big is the L2 Lagrange point? (i.e., how closely do you need to be for an orbit around L2 to be practical?)
> How big is the L2 Lagrange point? (i.e., how closely do you need to be for an orbit around L2 to be practical?)
The L2 point doesn't really have size, and even its location isn't stable. It's a mathematical point, and when we say "orbit around L2" then that is not fully true either. The spacecraft are on what's called "halo orbit" - maybe imagine balancing a steel ball (like from a bearing) on a bottle that's sideways, it's probably easier to roll and balance the ball lenghtways of the bottle, than on rolling it sideways. The best analogy I could come up with. You don't want to be too close to the L2 point, as then the orbit would be very short and less stable, think of it as having a smaller bottle - probably harder to balance the steel ball on a smaller bottle than a big one.
> How far away PLATO will be from the James Webb Space Telescope?
Probably on the magnitude of hundreds of thousands of kms on average. Interesting question though, hopefully they won't get too close :D
Let me remind you guys that "just 20 light years" = roughly 200 trillion kms. At the speed of voyager 1, it takes roughly 1600 yrs to travel 1 trillion kms. 200 trillion kms would take 320,000 years to reach there. Even if you increased the speed of voyager 1 by 10 times, it would still take 32000 years to reach. We really need to up the speed by a factor of 10000 before we can get anywhere close to human lifetime achievable travel times.
Accounting for acceleration and deceleration seems like an unspoken obstacle in your timeline. How can a human comfortably accelerate or decelerate at a rate greater than 9.8m/s^2 for long periods of time? “Hey guys, we will need you to pull 9Gs for the next seventy years as your ship slows down to enter a stable orbit”
Accelerating consistently at 1G (and then -1G for the second half), should take 6 years of proper time (from the perspective of the traveller) to get there.
Yea, actually the problem is not at all that we’d need too much acceleration for the human body. Accelerating at 1g for a couple years gets you to preposterous speeds (and we don’t even need any artificial gravity nonsense!). The problem is that accelerating at 1g for years would require a ridiculous amount of energy.
In his 1958 juvenile novel Have Spacesuit, Will Travel (I read it years later as a tween), Robert A. Heinlein described this as a "skew-flip maneuver" that would get someone from Earth to Pluto in five days at 8G (!). And apparently E.E. "Doc" Smith described it even earlier.
I don't think we'll be sending humans on these kinds of missions. We'll be sending AI systems (ship, bots, etc.) and then waiting millennia for them to report back.
It's conceivable that we could send the seeds of humanity and other terrestrial life — along with AI systems capable of raising it, terraforming the planet as necessary, and building a society.
We might not ever travel there or receive guests from New Earth any time in the foreseeable future, but it's fun to imagine that one day we could have a colony of distant pen pals separated by only 20 years of latency.
How fast could a ship get going with a RTG powered ion engine like AEPS? Rough back of the envelope figures come out to 100 years to cover 1 light year, or a few thousand to reach 20 ly out, which is... nothing like science fiction books but not impossible either.
> before we can get anywhere close to human lifetime achievable travel times.
Humans are an intermediate step. We are not the final shape of earth-origin intelligence.
Why would we continue to fill these bodies when we develop the tech to no longer be so limited? Constrained to the parameters of our gravity well and to short lifespans without backup?
Or maybe we just get replaced outright.
Or, the worst outcome, everything from this planet dies without ever having left.
You can’t develop tech to move intoto a computer. Although it’s a good book idea.
A kool-aid style cult where they convince their followers they will be “uploaded” once they hand over all their possessions. Then they just get shot in the head.
AI might do it, but I wouldn’t count that as us going there.
Realistically if we perish and there is no comparable conscious life then no one can even care whether a bunch of machines we spawned to assist us continues to exist.
Thinking 'it is good' is a product of your consciousness. When there is no one to judge then there is no 'good'.
It's murky concept though, so I wouldn't bet on mind uploading in our lifetime.
Some fairly fundamental things need to be answered first. Things like how does consciousness and the sense of self arise.
Naively, if you think that you are just a program that runs on a bunch of neurons in your brains, and that this program can be uploaded to a computer, you are still left with a very annoying problem: you upload a copy, and leave the original running in your squishy brain. So what then? Do you kill the original? But that involves killing a living and breathing human being. Do you wait until it dies naturally? That's still not a good answer, because you have to die so that a copy of you can continue existing.
So until we figure how to actually "teleport" our consciousness to some other host, we are in a pickle. And there's absolutely no evidence that we'll ever be able to do this teleportation. What if we never figure out the physics to do this?
Edit: I suppose you could sidestep this by generating fully digital consciousnesses that mimic what a human brain does. So a fully digital human. Assuming we can brute-force simulate a real human brain, this should be at least physically possible (as opposed to teleportation), but this still raises philosophical questions. What you are generating then aren't human beings, but conscious AI. You could argue that the human race would eventually be supplanted by immortal AI that are no longer bound by biology, but I'd argue that this isn't an evolution of the human race, rather a completely new life form (if you can call it that), which has nothing to do with humans except that we created it.
You're imagining a future that is a continuation of our lives here and that is kind to currently living humans. But this is just inventing requirements.
Imagine none of what you've presumed is necessary is even a design objective. Maybe it is, but probably it's too difficult and uneconomical. These capabilities could be built without ever enabling any of us to live or achieve immortality.
Those hypothetical digital beings could be human-like, maybe exact simulations, or perhaps totally different. They could be benevolent, or perhaps not. We might come to a conclusion that it's no longer ethical to have biological humans. Or maybe we're forced into that outcome.
Who knows. This is all wild postulation. But one thing that might happen is runaway growth and a deviation from a world we're familiar with.
I’ve never understood the idea that humans should be doing space exploration. Especially given the proof that robots and machines are demonstrably better and more suitable for these kind of tasks by such a degree that they dominate off-planet sensors-effector combinations.
Making space exploration comfortable for humans instead of creating TARS like intelligent machines (possible in our lifetimes imo) foundationally limits and constrains the ability and scale of exploration.
Seems entirely egoistic and anthropocentric. Is there any alternative reason - other than stated - as to why humans should be considered the best candidates for these tasks?
I wonder if space exploration will turn out to be no different than mountain climbing. There's nothing useful on the mountain, we can't live there, it's purely exploration, sport, and a feeling of achievement.
By far the most motivating part of high dangerous mountains is the internal journey of climbers to have confidence in your own skills and training to overcome any obstacle that can happen. Then facing an unpredictable challenges, trusting your teammates if you are not solo, overcome them or knowing when to retreat to safety.
Facing semi-continuous fear of death, not getting hampered it but calmly assessing it and acting accordingly is a great skill for any aspect of life. Overcoming oneself mentally, pushing and redefining our own limits (normal folks have them mentally set very low compared to actual threshold) is the gist of it.
All this and much more while being mentally degraded to 10-20% of capacity at sea level. in environment where 1 mistake can be easily the last one. Physical capacity is also greatly reduced, and you climb very steeply or almost vertically, with 10-20kg backpack, sometimes more. Doing this even for weeks without break. Summit push can be easily 48-72h 100% effort without a sip of water, any food nor sleep, after all I've written. I wouldn't even call this 'sport', you don't call early Antarctic expeditions a sport, do you.
I don't see why almost all of this and much more shouldn't be present in space exploration, just environment will be a bit different (but views on myriads of stars remain).
Humans generally do things out of their own self interest (which for a lot of people includes improving the living conditions of their descendants). So, if humans aren’t going to colonize space, we’ll either need somebody who… just sort of likes colonizing space with robots? Like as a hobby I guess?
Or maybe we’ll have robots at some point capable of working in their own self-interest.
If these robots find a good target and make it habitable, then you would still need to send humans at some point, right? But then you sort of wasted all these thousands of years by doing robots first, you might as well send humans too.
The existence of the Super-earth was not directly observed, but was instead inferred by the gravitational lensing of all the democracy[0] being spread in a sphere around the planet.
We know that, due to the lack of observable galactic civilizations, if there is a Space War For Democracy, it is a Shadow War [0]. Perhaps with one exception [1].
in Vernor Vinge's novel A Deepness in the Sky the alien planet freezes for part of the year and the intelligent aliens have evolved to survive being frozen and thawed. One group develops technology to say unfrozen while their enemies are frozen and this gives them a huge advantage.
Great book and I highly recommend it. Also has concepts of realistic mind control that is VERY creepy and the ultimate in distributed computing based on smart dust.
Ya' know, Oly was very happy to find his farm was in Iowa, rather than Minnesota. When his friend Sven asked him why, given that taxes were higher in Iowa, Oly replied "Vell, now I don't have to put up vith those lousy Minnesota vinters no more!"
Life in that planet evolved to essentially hibernate during their long winter. Presumably the processes that resulted in the very earliest life forms happened countless times until some surfaced that had that feature.
> Its distance from its star changes significantly, causing the planet to move from the outer edge of the habitable zone to the inner edge throughout its year
The habitable zone is defined as the area around a star where liquid water could be found, there is no "our" habitable zone and "their" habitable zone.
Parts of our own Earth aren't in the habitable zone, by that definition. Even here we get big surprises - undersea vents were unexpected oases, microbes miles deep underground, microbes living in boiling water in Yellowstone...
Not all life in the universe may require liquid water, nor require it 24/7. In our own solar system, some planetoids outside our supposed habitable zone likely have some liquid water - Europa and Enceladus, for example.
> Parts of our own Earth aren't in the habitable zone, by that definition.
What parts would that be? Even the polar caps have huge liquid water oceans underneath. Unless you’re talking about the mantle or molten core, there are no uninhabitable areas on earth as per astrobiology (not even miles underground).
> Not all life in the universe may require liquid water, nor require it 24/7.
You might as well be talking about leprechauns and unicorns and Horta. Water is the universal solvent and has at least five unique properties that are as critical to life as carbon’s ability to form four chemical bonds.
You’re correct that moons experiencing tidal heating can contain liquid water, but that’s irrelevant to a planet. The habitable zone is specifically talking about planets (rocky ones at that), not any arbitrary satellite. It’s a term of art in astronomy, not a colloquialism.
> Unless you’re talking about the mantle or molten core, there are no uninhabitable areas on earth as per astrobiology (not even miles underground).
We've found microbes that can survive at 120 Celsius, -25 Celsius, very high and very low pH, large amounts of ionizing radiation, intense pressures, etc. Habitability is a wide range encompasing scenarios not conducive to liquid water.
> Water is the universal solvent and has at least five unique properties that are as critical to life as carbon’s ability to form four chemical bonds.
None of that rules out life on other chemistries. It makes water+carbon-based life the most likely scenario on planets with liquid water, but hardly rules out other potential biologies.
> You’re correct that moons experiencing tidal heating can contain liquid water, but that’s irrelevant to a planet. The habitable zone is specifically talking about planets (rocky ones at that), not any arbitrary satellite.
But we should absolutely be looking at planet-sized moons with potentially habitable conditions, which we believe to be quite common. They are, after all, more common than the single "habitable zone" planet even within our own system.
Is the upshot of this observation supposed to be that PLATO should change its plans and direct its telescope in a different direction because it has more promising places to look than the habitable zones around stars?
If not, and if you can understand why it's prioritizing that, then why do you take this definition of habitability to be tantamount to denying the possibility of discovering other forms of life? For those possibilities to be relevant to a research program, they need to be motivated by something more than "gee, hey, you never know."
So it's not for lack of reflection on those possibilities that we arrive at this operative definition of habitability. There are pertinent reasons for moving forward with this definition that don't amount to denying other boutique possibilities. Construing it that way I think is just an uncharitable interpretation.
It’s not impossible, but we’ve got a ton of evidence why it’s extremely unlikely. It’s a long list including stuff like possible quantum transition states enabling biochemistry, reactivity with oxygen (the third most abundant element), and spectroscopic transparency. It’s an active area of research that keeps coming up with dead ends.
Ammonia and methane are the best candidates but those would only be possible at low temperatures that preclude lots of other reactions.
And none of those smart people have come up with any experimental evidence that it’s actually possible. No equivalent to amino acids or nucleotides or saccharides or… the list goes on.
I’m not talking about SETI, I’m talking about basic chemistry experiments. There are tons of experiments that can spontaneously form amino acids and nucleotides, even way outside the parameters normally considered habitable.
There is tons of concrete evidence, you’re just ignorant of it. Start with Stanley Miller’s seminal 1953 paper “Production of Amino Acids Under Possible Primitive Earth Conditions” and go from there. There’s been a lot of work on the topic since then, several of which have made it to the HN front page.
> Hemoglycin (previously termed hemolithin) is a space polymer that is the first polymer of _amino acids_ found in meteorites.
I’m done, have a great day! (Monomers)
Edit: My apologies for being dismissive. I’d like to get into the specifics of why amino acids (amino and carboxylic groups specifically) are special, and interesting exceptions like hydroxy and alpha-hydroxy acids, but I’ve got to get to work and I could spend an entire year explaining the nuances. The deeper you get into the details, the more the anthropic principle rears its ugly head.
> ammonia-based life form at our stage of exploration is probably gonna scoff at the idea of scaldingly hot liquid water
Ammonia-based life exists within water habitable zones; Mars is within our Sun’s conservative habitable zone [1]. (Also, “ammonia boils at 98°C instead of –33°C” at “60 atm, for example, which is below the pressures available on Jupiter or Venus,” meaning “ammonia-based life need not necessarily be low-temperature” [2].)
One reason to suspect ammonia-based life is rarer than carbon-based life is the universe contains a fifth of the nitrogen that it does carbon [3]. (This is why silicon-based life is also almost written off.)
> The two examples you gave... Include liquid water.
This specific planet spends half its orbit in said zone. Here on Earth, we have creatures like https://en.wikipedia.org/wiki/Mudskipper that can survive severe dry spells, and fish that can happily freeze sold in ice for months.
Europa spends zero time in our solar system's "habitable zone", but because of its conditions, may still possess large amounts of liquid water. It's a perfect example of why the "zone" may be overly narrowly defined, even for Earth-like water-dependent life.
> It is entirely possible there is some other form of life that does not require liquid water, but we have yet to discover it.
And we certainly won't if we only look in Earth-defined "habitable" zones.
You seem to be deliberately trying to pervert the definition of habitable zone.
Just because there are regions on a planet in the habitable zone that contains ice does not mean it is not in the habitable zone. If it were further out beyond the habitable zone, there would be no liquid water at the surface.
To quote my friend Andy Dufresne, "How can you be so obtuse?...Is it deliberate?"
> You seem to be deliberately trying to pervert the definition of habitable zone.
They're fine. Some people here are trying to overextend the definition and it's good to push back.
The habitable zone is about surface water. Pointing out that parts of the earth lack surface water for extended periods is a really good analogy to a planet that drifts in and out of the habitable zone.
Earth is the only environment in which we've found life, so it makes sense to first focus on other Earth-like planets. Your point is not without merit but taken to the extreme it would be like sending exploratory teams to the Mariana Trench to look for un-contacted human tribes.
We have incontrovertible evidence that water + carbon + time sometimes equals life. We have no evidence of any other non-carbon or non-water chemistries resulting in life so why wouldn't we focus on locations potentially rich in water and carbon first?
The first exoplanet detection was in 1992; in my lifetime, "there are no planets outside our solar system" was roughly as supportable as "there is no life outside our solar system" is today.
You seem to be talking past everyone else in this thread because nobody has disputed a single thing you've said however you're ignoring (perhaps unintentionally) the basic statistical reality that if we focus on potentially water- and carbon-rich environments we are as a matter of course more likely to find life sooner.
But the "basic statistical reality" is also "there are a lot more known/accessible planets outside of the zone in which liquid water exists naturally on the surface", which leads to a quantity vs quality consideration for which we don't have enough information to decide right now.
Yes but "we don't have enough to decide" means you have to lean on the single data point you have, not completely ignore it and just try to look everywhere all at once. You have to focus your finite resources and "just pick something" isn't a reasonable path when there's more things to investigate than we could do in 10 lifetimes.
> Or maybe we start with what we know (carbon-based)
But we know more than one thing. One of those things is the Fermi paradox - that the universe should statistically be full of evidence of life, and yet we struggle to find it. That may be evidence we're making the wrong assumptions.
> keep our minds open to other possibilities...
Yes, and I'd argue that means including scenarios like Jupiter's moons in our search. (As a bonus, Jupiter-style planets, being larger and far from the star, are substantially easier to find.)
Like you said, the first exoplanet was detected in your lifetime.
We haven't even had the chance to fail yet, the Fermi paradox is not yet in play when we're considering essentially our first move. To extend an analogy from further up thread, it'd be like looking in the Mariana Trench for un-contacted human tribes after taking a quick glance around the neighborhood and deciding there's nothing else to be found anywhere else.
There's a meaningful operative definition and you're muddying the waters over that definition on the grounds that, hey, who knows, maybe it's different somewhere in some way.
I just think you're confused if you think that observing a specific definition of habitable zone is tantamount to a specific denial of that possibility.
I'm not confused by its definition, I just dislike the use of the term. It leads to significant confusion in laypeople - "they found a habitable planet!" is something I've heard breathlessly repeated multiple times, and "but Earth is so perfectly placed, it can't be by chance!" used as an argument for creationism.
Regardless of the official definition, the word “habitable” is highly subjective. Extremophiles like tardigrades can survive being frozen and/or completely dehydrated. A planet with an eccentric orbit like this one could hypothetically support species capable of entering some form of extreme hibernation during part of their year.
And that's fine, but when communicating outside the speciality, I'd really like to see some other term used.
https://www.cjonline.com/story/news/politics/government/2025... for example says "Kansas tuberculosis outbreak is now America's largest in recorded history", where "recorded history" is apparently the CDC's "term of art" for "since 1950", which isn't what a layperson hears.
The IAC is communicating outside the speciality here, via a press release.
That's why the article's breadcrumbs say "Home > Outreach > News".
We saw the same issue during COVID - scientists talking to the general public often talk like scientists instead of science communicators, and that causes people to misunderstand. Fauci's "no evidence" (yet) masking prevents disease incorrectly becomes evidence masking can't prevent disease.
Not many uninterested laypeople are going to be browsing the IAC website for astrophysics news. People that are interested should probably familiarize themselves with the terminology commonly used in astrophysics.
Once it makes its way to PBS Space Time, sure, maybe you avoid terms of art. Or explain the particular definition when it is first introduced.
That's just my opinion anyways. I always try to familiarize myself with the common terms of art when learning about a new discipline.
> Not many uninterested laypeople are going to be browsing the IAC website for astrophysics news.
But they will get linked to it, or read articles by reporters using it as a source without enough domain knowledge to make the distinction. I, after all, didn't seek this out - it just popped up on the HN home page.
> What seems weird to me is to be interested in a discipline, seek out news and conversation about it (from university press releases!) but then reject and/or argue about any terms of art that are established within that discipline.
I think science communication, post-COVID, needs to take a serious look at how to better explain things to the public. "Habitable zone" is simply one example of it.
I edited part of that out, because I actually do broadly agree with you regarding science communication, and realized my comment was a bit stronger than I intended. Looks like you were quick on the quote!
However, I think there's some serious slack to cut when you're viewing an article on the Institute of Astrophysics website, compared to reading Fox/CBS/whatever.
Edit: In my re-reading of the article, I see they define it! I'm no longer sure what all this back and forth is even about. "This orbit places it within the habitable zone of the system, _meaning it is at the right distance from its star to sustain liquid water on its surface_" Do you want them to not use the term even when they define the term?
> Do you want them to not use the term even when they define the term?
Yes, I do. I think it's a needlessly confusing term to use in stuff intended for public consumption.
For a similar example of the issue, I often get radiology reports in my healthcare provider's portal. My dad is a radiologist and they're still quite scary/bewildering to read - they frequently use various terms of art for "looks fine and normal" that sound terrifying.
That was all fine when the intended audience was other doctors, but these days I can pull them up myself. I at least know enough to not freak out and ask my dad; many don't.
I don't want to see NBC/BBC/NYT articles using the term, and that means being careful with the sources from which they receive their info.
While it's possible for conditions for life to emerge or sustain itself to be present beyond the habitable zone (e.g. there's likely a subsurface ocean orbiting the farthest plant from the Sun on Triton), afawk it is more probable that life forms in the habitable zone. That is the only one we have a data point for.
The terminology was probably chosen specifically to be somewhat clickbait, so it's probably not worth picking apart the words "habitable zone".
The core idea really boils (heh) down to water, _i.e._ the "universal solvent". You can certainly argue that liquid water may not be necessary for life, but it's hard to argue that water's presence isn't a decent prior for potential life.
But directly detecting liquid water in extrasolar planets is _hard_. So we do the next best thing and try to use whatever indirect signals we got. We know that liquid water can only exist within some range of temperatures and pressures. So let's just start with temperature.
What things can affect the surface temperature of a planet? Amount of energy received from the parent star (i.e. stellar irradiance), geothermal heating, tidal forces between a moon and planet, and probably many others. Stellar energy stands out as being the biggest contributor of energy and, fortunately, the easiest one to measure.
Of course, you could have localized sources of favorable conditions, like thermal vents or whatever, but those kinds of things are _way_ beyond our ability to detect with current tech.
So, we've narrowed down our focus to _one big contributing factor for potential life_, the amount of energy received from a planet's host star. But how can we relate energy to temperature? This is effectively where all the physics and astronomy come in via thermodynamics, orbital mechanics, and stellar physics.
Suffice it to say that all the effects combine to give a range of possible orbital radii and planet sizes where liquid water has a good chance of existing on the planteary surface.
This range of radii and planet sizes is the concept that matters. The name for this idea is "habitable zone", which suggests why we might care, compared to the more precise "orbital and planetary mass parameters favorable to liquid water formation at average planetary surface".
This kind of resource variability seems likely to favor the development of intelligence, so there’s that.
But I m sure we will find that the planet has issues that make complex life unlikely, just on a statistical basis.
Simple life seems increasingly likely to propagate through panspermia, based on what we find deep inside the crust of our planet. Life forms that feed off of radioactive decay especially seem promising for panspermia.
I wouldn’t be surprised at all if we discovered that for habitable zone, earth-like planets , the presence of simple life forms deep inside the crust turns out to be the rule rather than the exception, at least in our corner of the galaxy.
My napkin math says the surface gravity would be around 30 m/s2.
I'm not looking forward to a visit. Maybe it has a large moon like Earth. If it is in the same proportion as ours, the moon might even be friendly to humans.
Ever pick up what you thought was gonna be a really heavy box and it turned out to be empty, and got briefly thrown off-balance? I'd imagine that, but for everything.
The moons gravity is 1/6 of the Earths. So looking at our moon visitors performance, a super earth visitor would probably be great at high jump but pretty shaky at anything else.
I wonder if jumping even makes sense at 6x gravity... maybe they would never have learned how to jump at all and always keep some limbs in contact with the ground.
Or if "humanoid" even makes sense. Something snake like that can spread out the pressure along a longer surface might be better. Or at least something with more than two legs.
They might have to be entirely aquatic at that point or perhaps have some very exotic skeletal structure that can support their weight. Perhaps ball shaped beings who roll around instead of any sort of walking? I'm unsure how would they deal with a small incline.
Weight lifters are able to lift 6x their body weights, but it's not a sort of load that we could profitably exist under long term. We'd need to have extremely thick limbs and at some point that won't help either because of the cross-section vs. weight scaling law. It's also a sort of weight where any kind of leverage against a joint will generate massive forces. E.g. try catching a 50kg falling weight, you are likely to dislocate your joints and/or break some bones. And yet 1/6 of that is entirely manageable.
If intelligent life exists on a superearth it would be trapped there because rockets wouldn't be able to reach orbit. In fact 1.4g seems to be the max that chemical rockets can escape. Maybe they could built an electromagnetic launcher on top of a absolutely huge ramp.
Or they would be forced to figure out technology that we would consider science-fiction, assuming it's possible. To consider our tech as the pinnacle is the wrong approach, I think.
Perhaps we've had it too easy here - moderate climate, oil as an easy fuel source, and gravity that isn't too oppressive. I wonder what technology would arise in a more difficult environment, such as this superearth.
Ironically I think you’d be more likely to go to space on such a planet. Imagine being barely able to jump, let alone fly. You would want to leave more than anything. It would be like a space race, against the universe.
I’m imagining some sort of mega cannon or railgun as a propulsion method to fling them off the planet.
I asked a physicist friend about this. At 6x mass, it would only be 6x the gravity if it was the same size as Earth. Depending on the density, the gravity could actually be weaker than Earth!
Yeah, not having the radius/diameter of the planet mentioned really hurts understanding the effect of that mass. However, I doubt it is like Saturn where it could float in water.
I'm sure the aliens reading that are saying "Thank god! They aren't coming here." :-)
But on a more serious note, this is some great science. I am super impressed by how sensitive the instruments need to be to chart the fluctuations due to mass here at 20 light years. I'm always on the fence about whether or not we should focus a beam of RF with some modulation on it in their direction, on the one hand it would say "hello! we see you!" on the other that might not be a good idea.
The Raleigh criteria for 1km resolution at 20ly requires an interferometer with a baseline of 120,000km. That’s about a third of the way to The Moon or 10x the diameter for The Earth.
How far away is such technology?
For 1000km resolution the requirement is three orders of magnitude smaller, or ~120km. Could such a device be terrestrial?
Depends on the radius, as I understand it. It could have more or less gravity depending on that, but we don't know what the radius of this planet is yet.
Wolfram Alpha has a good calculator if you want to play around with this [0]
At 99% the speed of light it will take the traveler less than three years, while 20 years passes on earth. If they then turn around they will return to earth, they will arrive aged 6 years while 40 years have passed on earth. You can come back younger than your children.
Which then makes for an interesting moral or ethical dilemma: is it ok to embark on such a mission after having children, knowing that they will live half a lifetime without you and, assuming you left before the age of 34, will be older than you when you get back.
Since each star is different, it seems like the inner and outer limits of each habitable zone would also be different for various stars. Is it just the mass of the star that determines this, or are there other factors?
Only 20 lightyears sounds good, and the elliptical orbit within the habitable bounds sounds also good, comparable to our summer-winter shifts. Now they need to detect water
Summer and winter on Earth isn't due to elliptic orbit, but the tilt of the planet. This planets orbit takes it both inside and outside the habitable zone on each orbit. That's very very bad. Going from Mars-like to Earth-like to Venus-like every year.
Not very bad per se. It would be summer and winter for the whole planet, in longer cycles. It didn't hurt the development of advanced civilizations on earth at all. You have pressure to adapt.
The only thing more exhausting than people acting like an election instantly makes everything great and the world is now going to be amazing is the people acting like it's literally the end of the world.
You will not be substantially better or worse off a half-decade from now than you would have been in a slightly different circumstance.
Honestly a really bad take given the current environment. This is the not the thread for it but I'll point out that just today funds families around the USA and world require to live were pulled out from underneath them, regardless of law. I have a child who depends on those funds so it impacts me greatly, and I don't know if that child will be around long enough without funds for her care.
So please do not minimize what people are going through, it may not impact _you_, but many people are negatively impacted by the insurrectionist taking over the USA.
Balance compassion for yourself and others. Finding the balance is really hard, maybe impossible to do perfectly, so you have to try constantly. When you get close, I think you'll find that negativity evaporates in yourself in a way that's infectious to those near by you. Take care.
Check out https://www.centauri-dreams.org/, it's a blog dedicated to interstellar travel. It's on hiatus at the moment, but there are plenty of back articles to read!
However, I recommend you figure out how to reduce your anxiety, because after reading it for a while it will become clear that interstellar travel isn't happening any time in the foreseeable future. Fortunately, I don't think that a species that flourishes from the hot tropics to the freezing arctic is likely to be in much existential danger from climate change, and even less from the volatile vagaries of politics. (Climate change might bring very substantial changes, but escaping off-planet isn't going to be less change)
"the new planet ... tak[es] 647 days to complete an orbit around its star, 40 days less than Mars. This orbit places it within the habitable zone of the system, meaning it is at the right distance from its star to sustain liquid water on its surface"
1. That orbit make it really cold relative to Earth - like Mars is.
2. It doesn't say that the planet has a human-breathable atmosphere; it might, but it might not - like Mars.
Also,
3. Gravity force is gMm/R^2 right? Let's say same density as earth, and that density is uniform. Now, the mass relates to the radius by R^3, so the gravity force will be higher by 6^{1/3}, or about 1.817x higher than Earth.
So, would you say this is a habitable planet? It's kind of a stretch.
So can we now have a trio of ulra large optical telescopes, flying in an ultra high resolution formation, used to create images useing optical interferometry, now. Now? Want!
And if the international astronomic comunity drags there feet , advocating for more "science" missions, and getting proof of exo habbitats befor they can look for them, tenures safe, then lets defund the whole mess, and build telescopes at scale, get optical data, and THEN they can theorise in they very own arm chairs at home, about all the anomalies they want.
I don't think this is a good take.
Discovery & science are inherently meaningful even if the applications are not immediately felt.
Nuclear magnetic resonance (NMR) was discovered in 1938, but there was no obvious applicability of it to everyday life. In 1971, 33 years later, Paul Lauterbur used it to develop the first MRI
"Intersecting" the habitable zone isn't the same as "within," I find it curious that discussion of the ramifications are far down, it seems pretty salient to me...
The idea of an ecosystem hence culture for which a fundamental cycle is a year of fallow hibernation followed by a year of fertile plenty is quite compelling as a scifi trope though.
Me I'd name the planet Persephone for this reason.
Just a reminder that if, for some reason, we discover technological civilization on that planet, it's very, very bad news for us as a species.
I'm talking about the Fermi Paradox. Basically, given all the stars we can see and that we see planetary systems around virtually every star we look at, then a decent portion of them should have rocky planets in the habitable zone. A portion of those should have the conditions conducive to life. A certain percentage of those will develop technological life.
Each of these steps that reduces the likelihood of technological life is called a "filter" in Fermi Paradox parlance. These vary from small filters to so-called "Great Filters". The idea of a Great Filter is almost no species gets beyond it. All the heavy elements we have access to might be a Great Filter.
As a reminder, anything heavier than helium is made in a star. Normal stars only make elements up to iron. It takes a supernovae or a neutron star merger to make elements heavier than this. So, for Earth to exist as is, there had to be a star relatively close to us that was the right size to basically go supernova. It had to be born, live and die before the Sun formed and that material had to be captured in our proto-planetary disk and ultimately become part of Earth.
We have thus far found absolutely zero evidence of these alien civilizations so the question is why? If we find an equivalent civilization to us on a really close neighbour then by Bayesian reasoning, it means it's significantly more likely that a Great Filter is still ahead of us.
For many reasons.
1 - it might be very unique itself
2 - it might be very close to us
3 - it might be orbiting a very interesting star, a star type we didn't expect to have that planet type or so many planets, or so close, or so far, etc
4 - the more exoplanets we discover the more we learn how star systems come to be. the more we know how rare ours is, how it might have formed, etc. It helps us answer age old questions.
The orbits of planets in our solar system are quasi-circular, with only Mercury (e=0.20) and Mars (e=0.09) being more elliptical. Every other planetary orbit in our solar system has e<0.05, even 0.00x for Venus or Neptune.
They're not perfect circles but close enough for all practical purposes.
Next year there is a plan to send a space telescope to L2 with the main objective being to search for Earth-like planets around Sun-like stars in the habitable zone.
Like Kepler and TESS telescopes it will use the transit method to find new exoplanets, but unlike any mission before, it's going to look at the same spot in the sky for over a year. Super excited to see what data it brings back to us.
The telescope is called PLATO ( https://en.wikipedia.org/wiki/PLATO_(spacecraft) )
I contributed to the project a few years back, very happy to answer any questions.
L2 as related to space telescopes was a new term to me, and turned out to be utterly fascinating. The Webb orbits the sun and periodically boosts velocity using Earth's gravity:
> The James Webb Space Telescope is not in orbit around the Earth, like the Hubble Space Telescope is – it actually orbits the Sun, 1.5 million kilometers (1 million miles) away from the Earth at what is called the second Lagrange point or L2.
https://science.nasa.gov/mission/webb/orbit/
The wiki on lagrangian points also has a bunch of useful info on this stuff. Gravity is absolutely incredible
https://en.m.wikipedia.org/wiki/Lagrange_point
Lagrange points are fascinating to me and I feel they are underrepresented in science fiction, compared to how the space age ahead of us may play out.
The events of human history on earth have revolved in great part around settling at or controlling strategically advantaged locations, for example any coastline, or a geographic bottleneck for trade and travel (think of Singapore and the Strait of Malacca).
A Lagrange point is the simplest space-based analog to this that I know of, if you want to put something in a fixed location relative to other bodies, the Lagrange points are places where you can do it with the highest fuel economy. Then when operating from that position you will have more energy available to do other things, granting you advantage over competitors who are not at the Lagrange point.
So whether it's science, research, trade, defense etc. there is a compelling reason to locate things at a Lagrange point, and it seems this is already happening as we have science satellites at L1 and L2 and I believe L3 has been talked about. The Lagrange points are not all created equal in terms of distance to their respective bodies, size, energy required to maintain a position etc. All two body systems have them, so for example the Earth and Moon have a set of Lagrange points that are significant to us.
The LPs are what a lot of our space politics and problems may eventually revolve around (quite literally!).
> events of human history on earth have revolved in great part around settling at or controlling strategically advantaged locations, for example any coastline, or a geographic bottleneck for trade and travel
Not only that, it's easier to send mass between Lagrange points than it is to send it to them from either of the orbital bodies.
Getting from Earth to L1 or L2, each 1.5mm km away, takes 15 km/s, escape + 12 km/s. (You have to fight both the Sun and the Earth's gravity.) Getting from L1 to L2 takes less than 100 m/s. (L1 to L3, L4 or L5 about 1 to 2 km/s.)
This confers strong defensive first-mover advantages; it's energy-wise easier to hold five than take one from the Earth. (Obviously, it's mass-wise easier from the Earth.)
Relays at L4 and L5 (also described in the linked Wikipedia) would be useful. If both are built it's reasonable for relay stations or satellites stay in contact continuously, if over different paths at different times of the day. The second relay station would also be useful if other objects naturally collected within the regions of stability disrupt communication.
Lagrange points are a key plot device in Iain M. Banks’s The Algebraist. I did figure out the location of the Dweller wormhole pretty quickly, thanks to thinking about how Lagrange points worked, but it is a great work of science fiction.
Regarding sci-fi; Joshua "Lagrange" Calvert did a fancy maneuver in Peter F. Hamilton's Reality Dysfunction involving a lagrange point that gave him that nickname.
I always wondered what kind of fun treasure might be hiding in the L4 and L5 points. And what kind of secret missions were already sent there by various countries to look for stuff. There could be whole precious metal asteroids sitting around!
There's a list of probes and telescopes that have been sent to the L1 and L2 points: https://en.wikipedia.org/wiki/List_of_objects_at_Lagrange_po... -- This includes Nasa's Genesis and Goresat, ESA's SOHO, and ISRO's Aditya.
It’s arguable that even the stuff we consider to orbit the earth like the moon is really orbiting the sun.
MinutePhysics did a great video on this: https://youtu.be/KBcxuM-qXec?si=VngVwXeRKFPjnh15
Hi, thanks for answering the questions in this thread, it feels like something out of a sci-fi novel. Do you know of any similar projects that a software engineer could contribute to in their free time? Could be of much smaller scale of course.
To what extent (if any) will this program be impacted if all U.S. federal grant funding is permanently cut? Are there U.S. funded components/researchers involved?
As far as I know it won't be affected at all, the project is almost fully funded from the European Space Agency. And it will most likely be launched with the European Ariane rocket.
All the more reason why humanity needs multiple space programs.
I’m sure that will come up next year when they privatize NASA.
You mean when it gets named as a subdivision of SpaceX?
I love it when the Press Secretary says Doge with a straight face while defending attacks by reporters
you mean make it like 10x more efficient and effective? I'm game.
10x more efficient in extracting wealth for its owner. Everything else is a myth.
Don't forgot that they'll slash all the pesky regulations NASA has in place to keep astronauts safe, saving taxpayers millions!
'Please watch this 5 minute ad to receive your next tank of oxygen'
> you mean make it like 10x more efficient and effective? I'm game
Different missions. SpaceX beats Boeing and Lockheed Martin. It does not have the skillset to build a James Webb or Europa Clipper.
I wonder, is there any human endeavor other than space exploration (and maybe an occasional particle accelerator) that works like this? Sure, a big factor in the history of scientific progress is its structural resilience against localized political and economical kerfuffles, but that's more of an accident of how discovery and innovation are done - in small increments, achieved near-simultaneously by independent people or groups around the world (only one gets to take the credit, though). Meanwhile, it seems to me that space exploration needs to be organized into a competition to survive and thrive. To make things weirder, it's not about regular market competition - it's about staying in public consciousness, through continuously one-upping each other by Doing Something Impressive, which ends up attracting funding to all agencies each time (and conversely, when things get slow on the impressive achievements front, funding starts to dry out).
(We had one dry spell after Space Shuttles were retired, and IMHO this one could've been fatal to the entire field. Thank $deity for NASA's funding of commercial launch services, and SpaceX surviving 2008 and taking advantage of it to get the Falcon 9 to work and effectively re-light the public interest again.)
I imagine this is a transitional period; we're past the times of Cold War - times when everyone poured ~infinite money into weapons programs and space exploration got to leech some of it off - and we're not yet seeing the bootstrapping of cislunar economy on the horizon. I wonder if there's a more sustainable way of getting through to the other end, because relying on public interest feels rather risky. And, again, I can't think of any other field that is in this weird position.
Yes. In the past long-range sea voyages worked exactly in the same way.
They were seen as little more than expensive intellectual curiosities and eccentricities. In fact even once we discovered the New World had Columbus not come back and lied his arse off about riches that existed there only by coincidence (as he'd seen nothing of what he claimed), it's entirely possible that would have been the last journey to the New World for decades if not centuries. And over those decades you'd probably have had more and more of the population believing we never even landed on a New World to begin with.
And it'll be the same in the future. Eventually humanity will become a multiplanetary species and more value will be generated off Earth than on it. And I think we're probably not that far away from such point, but we live at a time when we will happily dump trillions of dollars to fund pointless chaos halfway around the world (that invariably just makes the world less safe for everybody), yet every penny that could take us closer to these species defining events is scrutinized like we're down to our last pennies.
And again - this isn't new. It's been the case for centuries and probably will be the case for the foreseeable future of humanity. It's easy to explain with a tautology - positions of power are held by those attracted to power, and those attracted to power are attracted to power. Once the New World became a means to power, that's when the 'trillions' started pouring in. The same will happen with space.
What a world it would be if he didn't lie his arse off eh?
Yeah I was really looking forward to that alt history where the Aztec Empire reached technological parity with the rest of the world. All hail Huitzilopochtli!
Technology wasn't the primary cause in the genocide of the Native Americans. The initial factor was the introduction of plagues to the Americas from the numerous intraspecies transmission that occurred in the old world as a result of the millennia of large animal domestication alongside high population density that had no analog in the new world (since there weren't the same variety of large domesticate-able fauna, apart form like alpacas or something). This is also why there was no American plague that spread in the other direction.
Western Europe was certainly not so far ahead technologically relative to the rest of the world as people so frequently give them credit for. Not until they had free reign over a new continent and purchased slaves to generate free money (*) and eventually total dominance with the advent of the industrial revolution.
(*) This also led to an arms race between rival empires and kingdoms in Africa and the stagnation of local craft and the eventual the economic collapse and political fragmentation of the wealthy empires that existed throughout antiquity and the middle ages - that have since been written out of history books. When the industrial revolution began spinning up out of the ashes and rubble of Christendom post-reformation, many other regions like the Middle East (for example the palace intrigue and power struggles within the Ottoman dynasties) and China (With the collapse of the Ming and ascendancy of the great Qing from the North) were similarly in crises - in part from indirect economic interaction with the growing powers in the west. It was then the nascent imperial powers found the world ripe for their exploitation and eventual hegemony.
Your time scale is so small. There are people alive today that witnessed the moon landing on television.
Galactic timescales are large. Plan for 10,000 years out, not tomorrow.
> Plan for 10,000 years out, not tomorrow.
I'm happy to. But then, like most people, I'm impatient, so I'll draw a second plan that ensures I get to see at least some of the cool stuff before I die, and then I'll get annoyed when this plan isn't followed.
Galactic timescales are large. Human lifespans are tiny.
Notably, 10,000 years is longer than all of recorded human history.
It’s a bit of a pipe dream to think we’d plausibly be able to follow through consistently on anything even 1% that long right now.
excellent, thanks.
What's the typical time scale for a transit? Also, why use transits instead of the Doppler method? Has this patch of sky been selected based on previous Doppler method star studies? Thanks!
> What's the typical time scale for a transit?
Generally measured in hours, or minutes. For example, if we were observing our system with perfect alignment, Earth's transit would be about 12 hours, Jupiter's transit around 29 hours.
> Also, why use transits instead of the Doppler method?
Quantity. PLATO can observe a sizeable portion of the sky at once, 100k+ of stars. With Doppler method the quantities are smaller + afaik there is a trade-off between number of stars being observed and the velocity we can measure. So to find Earth-like planets around Sun-like stars, we would likely have to go one or a few stars at a time.
> Has this patch of sky been selected based on previous Doppler method star studies?
I am not actively involved anymore. So I am not sure if they have already picked what part of the sky they PLATO is going to be observing. The previous Doppler method (aka as radial-velocity or rv method) star studies play a role, not only because if there's one planet, there might be more, but also because rv gave information about the star. However, keep in mind that this is to find new exoplanets, less to find out more data about existing ones. Rv will definitely be used along side PLATO, to confirm and gather more information about exoplanets that PLATO finds.
> Earth's transit would be about 12 hours, Jupiter's transit around 29 hours
…per year, for Earth; per ~12 years for Jupiter is I think what the GP was asking.
This is extremely dependent on the radii of the inner and outer limits of the the habitable zone for any given star, though, as well as the star’s mass.
Both are relevant! Thanks!
Radial velocity surveys require so damn much light, and such a complex precision spectrometer that they're only used on the very largest 8m-10m class telescopes on the ground, shooting in near infrared through the most advanced adaptive optics (or even interferometric modes) in great weather, pointed at a single target for a long period of time (this is a big deal), with a focus on super-Jupiter to Jupiter class objects in tight orbits.
The next generation of 30m class telescopes will be an order of magnitude more capable for the RV method, but even then you're not really going to be able to get fast locks on Earth analogs.
The RV method is vastly superior for detecting the planets we really care about - high confidence nearby Earth analogs. The odds of a transit being in the right plane for us to observe are tiny. But if we want to run a survey like that like it really matters (let's say a Solar system catastrophe hits a thousand years from now and humanity wants interstellar diaspora), we'll be studying the nearest thousand stars with the RV method using significant numbers of 100 meter class telescopes, or perhaps big space based interferometers produced in mass quantities, for decades.
What transit studies like Kepler do is study a small patch of crowded sky (most of the stars being very distant) with the sensitivity for very rare in-plane Earth analogs, in order to get a representative sample. When I was born we couldn't say with any confidence that planets around other stars existed, post Kepler we know that they're common. We can perform these surveys even with the shoestring budgets current governments afford astronomy because even if the odds of successfully detecting a planet that does orbit a distant star are very low, we can watch a million stars at a time.
You can find much less massive planets with the transit method.
The Doppler method relies on the planet pulling on the star to change the star's line-of-sight velocity periodically. Because planets are much less massive than stars, the star doesn't move much. You can only find massive or close-in planets with this method.
The transit method is much more sensitive to small planets like the Earth. It's true that the smaller the planet, the less of the star's light it blocks, so it's still easier to detect large planets than small planets using the transit method. However, it's much easier to detect small changes in a star's apparent brightness than it is to detect small shifts in the star's velocity.
There are a few different viable methods of detecting planets. Each has its strengths and weaknesses, and astronomers use all of them.
Very cool. Got a silly sci-fi question for you. IIUC, with current technology it would take on the order of tens of thousands of years for a vessel to physically travel to the closest known Earth-like planet (correct me if I'm wrong).
So any thoughts on what kinds of hypothetical breakthroughs would be needed to make the trip doable in (say) less than a human lifetime?
And related, what do you think about the plausibility of the [Breakthrough Starshot](https://en.wikipedia.org/wiki/Breakthrough_Starshot) initiative? Aware of any alternative approaches?
A different stab at this is to ask what it would take to build a telescope that could image some of these Earth-like planets, a project that turns out to be easier (in a very loose sense of that word) than sending cameras there.
The idea is you send a camera very, very far out in the Solar System (hundreds of AU) and then use the Sun's gravity well as your lens. Neat stuff and, unlike the interstellar probes, potentially doable in our lifetime.
https://en.wikipedia.org/wiki/Solar_gravitational_lens
Normally, diffraction and the effective aperture are what limit optical resolution. How does that work with gravitational lensing? Does the effective aperture become the diameter of the sun?
I'm too ignorant to answer that, but the technical paper here [https://arxiv.org/pdf/2002.11871] goes into a wealth of detail, and includes an image of Earth as it would appear to such a telescope (before and after post-processing) from 30 parsecs away. The optical properties of the solar gravitational lens are pretty astonishing.
Self replicating automata as described by Von Neumann able to repair and duplicate themselves, and other things like electronic components. ICs keep getting faster (so far) but use smaller and smaller features of silicon and could wear out from metal migration and all components will be under much more cosmic radiation than on earth. This makes a large shield of heavy material on front of vehicle to minimize this effect but that increases the energy/fuel needed. The space shuttle only took maybe week long trips but it had four computers for flight control , three extra in case of failure in different parts of the shuttle along with IIRC a separate backup backup computer in for use as last resort.
* Research faster interstellar travel, especially using something like a Buzzard engine to utilize interstellar hydrogen as resection mass. Required nuclear fusion power plants / engines and ridiculously strong magnetic fields; both seem attainable.
* Slow down human body metabolism and allow humans to stay asleep at near-freezing temperatures for a long time. If bears and chipmunks can do it, chances are humans could learn it, too.
* Invent sets of machines that can reliably self-replicate, given most basic inputs like minerals, water, and sunlight. Advanced semiconductors are going to be the tricky part.
* Study psychology, sociology, history, game theory, etc, so that the early society that will form on the new planet, isolated from Earth, would avoid at least some of the pitfalls that plagued human history on its home planet.
>Slow down human body metabolism and allow humans to stay asleep at near-freezing temperatures for a long time. If bears and chipmunks can do it, chances are humans could learn it, too.
The thing is - our current bodies can't live in space for long. So either we will have to build new bodies for us somehow or build a ship that can have gravity inside and protection from space outside (and we are talking about very heavy protection here)
In any other case there is no point in slowing down metabolism or whatever. You will die rather soon.
With a big enough ship, pseudo-gravity can be easily produced by rotation, especially if we expect the crew to spend 95% of time asleep.
> Buzzard
That's a bird, the engine is named after a person and is spelled differently:
https://en.wikipedia.org/wiki/Bussard_ramjet
Also, it won't work unless scaled up to the sort of thing only a Kardashev type II could do — 4000 km diameter — and at that level you've got other options that mean they probably won't:
https://arstechnica.com/science/2022/01/study-1960-ramjet-de...
The reason being the interstellar medium is way less dense than we thought in 1960.
Time dilation means that the closer you get to the speed of light the less time you experience passing. So even a 12000 year long journey as seen from earth, if moving fast enough, could feel to the travelers like a much shorter amount of time.
Yes, but practically with todays technology there is no feasible way of getting to a speed where time dilation matters over that distance, we run out of fuel so we need some external power source like a laser or solar wind that have other issues, iirc one only gets to 2x time dilation at 0.9 c. That’s a lot of acceleration.
We need to think about where we want the knowledge and what knows it. We could use humanoid AIs. We could hatch humans "just in time". Run them in a sim to 18 then release them on their mission. Ethics would need to accept this. Maybe we would be happy slowly expanding across the universe and an decendant talking to 'the aliens'.
I am not totally serious. But you wanna meet aliens? Gotta do something a bit radical.
If you haven't, you should read Accelerando, it's a collection of short stories IIRC that were put into a novel by the author. I didn't want to start with that, but that is in there. :)
If I may suggest another read: Perfect Imperfection by Polish author Jacek Dukaj. It's definitely weirder, than Accelerando, as the book drops you straight into the last parts of evolution curve, but definitely worth reading if you have liked Accelerando.
The story is super weird, but what I found out is that piecing together a picture of a far-future society from this story was very exciting.
My one-sentence review of Accelerando is "VASTLY better than the first couple chapters will make you believe."
I'm reading Accelerando right now and there's some unnecessary weird sex stuff at the start.
Good book despite that though, some very interesting ideas.
I imagine fuel isn't that big a problem until you care about being able to decelerate once you arrive.
And we don't have to send people, we should do our job as a Von Neumann probe and send frozen rna to distribute across the surface.
In space culture this is widely considered a dick move.
and in that 10,000 year blink, a civilization progresses from bronze metalworking to digital computers, awaiting our arrival
Can't pulse nuclear get there? Or does it require antimatter catalyzed fission?
Why is it pointing at the same spot for a year ?
Is it to get a more exhaustive survey single star or can full of stars? Or does that help it find smaller/further/different planets?
And how do they pick where to point at? Is there a way of guessing the likelihood of finding a planet?
The second dip, if roughly identical to the first dip in parameters, gives us the orbital period of the star. So now we wait a second period in order to observe the expected... Third dip, which confirms the planet if it occurs with the same parameters at the expected time.
Though I think that such observations would require at least two years, and up to possibly four years, for stars with orbits of periods similar to our own. I don't believe that a single year is long enough.
> Though I think that such observations would require at least two years
It is at least two years at least if I'm understanding this⁰ correctly:
Observational concept
Ultra-high precision, long (at least two years), uninterrupted photometric monitoring in the visible band of very large samples of bright (V ≤11-13) stars.
⁰ https://sci.esa.int/documents/33240/36096/1567260308850-PLAT...
I should have been more clear in my original post. AFAIK there are two options on the table - looking at two fields, both 2 years OR looking at one field for 3 years and then doing "step and stare" for the rest of the mission. Step and stare being that they "step" into a new field, "stare" at it for some time, and repeat.
Great questions.
> Is it to get a more exhaustive survey single star or can full of stars?
PLATO will look at 100k+ stars at once. And for most we will be unlucky to see a transit between PLATO and the star. Geometrically it won't align - imagine the star systems being in different angles from us. To bring an analogue - Take a pack of cards and throw them in the air, and take a quick picture while they are sitll in the air - how many cards will be facing the camera exactly with their edge. For us to spot a transit, the planet has to pass between us and the star. If the orbital plane is not parallel to us, we will miss the transit. So that's one of the reasons why it helps to look at bunch of stars with transit method. We expect that about 1% of the orbital planes will be aligned so that we can get meaningful data.
> Or does that help it find smaller/further/different planets?
Imagine you are trying to find Earth from another solar system. The longer you look at our Sun the higher the likelihood that Earth will pass between you and the Sun. And once you get lucky, and the Earth transits between you and the Sun, the brightness of the Sun only dips about 0.01%, so that means that in order to find small planets we have to have sensitive instruments and little noise, so that the dip in brightness can be measured. Furthermore, as the planet passes the transit and continues on its orbit, the perceived brightness of the star will increase, due to the planet reflecting some extra light. Measuring that can gives us some rudimentary information about the atmosphere - e.g. if a small planet reflects a lot of light back, maybe it's covered in clouds or snow.
> And how do they pick where to point at?
There's a whole complicated process to find consensus on where to point. Basically they look at spots that have lots of stars, and they look what type of stars they are. Here the objective is to find planets around Sun-like stars, so they would prioritize fields that have more Sun-like stars.
> Is there a way of guessing the likelihood of finding a planet?
It seems that some stars are more likely to have planets than others.
Since I have your attention - I figure this is still the best condensed ELI5 explainer of the history and methods used in search for exoplanets, and I keep sending this to anyone remotely interested in the topic:
https://www.youtube.com/watch?v=gai8dMA19Sw
(I also consider it to be the only true, original, canonical rendition of the Alladin song.)
It gets into the transit method around halfway through (at 3:43), and makes it glaringly obvious why this is the way to go, over tracking Doppler shifts. Still, this video is almost 8 years old (and neatly coincided with discovery of additional planets around TRAPPIST-1) - I wonder if there are new methods at play that are not covered here, and of course if the middle part still corresponds to how things are done?
You said: > We expect that about 1% of the orbital planes will be aligned so that we > can get meaningful data Somewhere below, someone used the figure of 0.01%. I assume they were mistaken, and your 1% number is about right for some "average" star sizes and orbits.
At any rate, that figure depends on the size of the star, and the distance from the star that the planet orbits--the further away, the smaller the chance that their orbital plane would be aligned with our solar system. For a Sun-class star, and a planet inside the habitable zone, what is the %? Am I correct in thinking it would be approximately 0.5/180, where 0.5 degrees is the apparent size of our Sun in the sky, and 180 degrees is of course half a circle (since it doesn't matter whether we're on one side or the opposite side of their star, hence 360/2). Which works out to about 0.14%, right?
How does the 0.01% look in comparison to the natural variability of star brightness, due to cycles, spots etc? Would that be a concern in terms of false positives? And also, given the specific line-up needed for us to see the pass, how likely it is for us to be able to observe the same planet in front of the star in the following years?
Stars do change their brightness in various other ways, but the light curve of planetary transit has a very characteristic shape. It causes the brightness to dim by a small but constant amount, with a (comparatively) very short and sharp start and end. A transit causes this pattern to occur at precisely regular intervals, and I don't think we know of any phenomena related to a star itself that would imitate the same effect.
Stars' relative positions generally don't change fast enough for the angle from which we observe a transit to change significantly. A transit of HD 20794 d is visible anywhere within a roughly 0.7-degree wide band. But our angular rate of motion with respect to the star HD 20794 is the same as its rate of motion in our sky, about 0.001 degrees per year. So the transit will most likely continue to be observable for decades or centuries to come, depending on exactly how the planet's orbit is aligned.
Would it be feasible to place telescopes at other orbital inclinations with respect to the sun in order to spot transits in stars that aren't within Earth's orbital plane ?
The orbital inclination relative to our sun doesn't really have anything to do with it. In fact, stars that are aligned with Earth's orbit are harder to observe, because they go behind the sun once a year.
Detecting an extrasolar planetary transit requires us to be aligned with the planet's orbit around its star. And since those stars are so far away, you would have to travel an immense distance away from our solar system to appreciably change the relative angle.
HD 20794 is about 20 light-years away from us, so changing our observation angle relative to it by 1 degree would require traveling about 0.35 lightyears. Our fastest-ever interstellar probe, Voyager 1, would take 5000 years to travel that distance.
Thanks for the clarification. You are absolutely right, in my post above I accidentally used the word "parallel" that caused the confusion. It wouldn't even be practically possible to use PLATO to observe them.
Here's a visual if that's helpful to any reader: https://www.researchgate.net/figure/Geometric-Probability-fo... .
>> Is there a way of guessing the likelihood of finding a planet?
> It seems that some stars are more likely to have planets than others.
to the best of my knowledge it has yet to be proved that any star has no planets.
Probably not the best choice of words from me there. However, there is a positive correlation between a star's metallicity and the number of planets a star has.
Your words are fine from my point of view, I am just tickled at the though of how hard it is to prove a star has no planets. Even with all stars having planets, it is worthwhile to carefully choose the field to maximize the chance of detection. Best would be if planetary disks aligned themselves in any predictable manner, but not much hope there.
Light collection. You want to observe one point for a really long time so you get a really good understanding of where the light is coming from, the properties of that light, and its behavioural patterns.
A lot of the detection is statistics around signals, so the better (read more thorough and coherent) your data (observations of changes in light), the more confidence you can have in your conclusions around what's causing the changes (planets with different atmospheres, different positions, different sizes and compositions etc...).
Many thanks! Comments like yours are what I love about HN.
How is the spot to analyze during that year of focus determined?
Sorry, I see this was answered in a previous comment: https://news.ycombinator.com/item?id=42855433
What was your contribution?
Figuring out the optimal placement of CCDs on Plato's 24(+2) cameras. Due to the way CCDs are fabricated, their properties vary a bit, they are not identical. For example, they can vary how much light they can hold before they become saturated. Given the high cost of fabricating these CCDs, and the fact that for each camera 4 CCDs are used, and all these 4 have to share front-end electronics, it was prudent to optimize their grouping to we maximise the dynamic range we get. More dynamic range means that we can tell more about the planets we find with higher confidence.
>CCDs
I think this is "Charge-Coupled Device"?
"an electronic sensor that converts light to digital signals through charges generated by bouncing photons on a thin silicon wafer"
Is that correct? Not familiar with the acronym.
Yes. In telescopes they use high-end CCDs with really big pixels for better light sensitivity and zero dead pixels.
This is a picture of the CCD array for the Gaia space observatory that used parallax to measure precise distances and slightly less precise angular velocities of billions of objects
http://www.bo.astro.it/~altavilla/FTP/GAIA/IMAGES/The%20comp...
Yes that's correct.
That's awesome! Are the multiple CCDs because you're taking photos in separate colors or something?
Good question. No, these will essentially be black-white "photos". The amount of light is measured. The reason for so many CCDs is so that the field of view would be as large as possible. A larger field of view enables to look at more stars at once. Given that we will be locked into looking at one spot for a whole year, it ups our chances of spotting something cool if we maximise the number of stars we are looking at.
However they won't be photos of planets really. It will be countless photos of the same stars over and over again, it's just that sometimes they will be slightly less bright than other times. Directly imaging exoplanets is incredibly difficult, but humans have managed it: https://en.wikipedia.org/wiki/List_of_directly_imaged_exopla...
Do they move the telescope over the year to account for movement? How is that calculated? Does this change with being closer to planets and their gravitational pull?
Asked from a total moron.
Yes, it's something that's referred to as pointing stability. The telescope will have star trackers to precisely know it's relative position - basically you make sure that you see the correct stars from where it is placed on the spacecraft. It will use reaction wheels to make tiny correction's to its position. Imagine you are in a computer chair and trying to spin yourself without feet or hands touching anything, just by twisting your body. Reaction wheels work on the same principle. As Earth completes a year around the Sun, the gravitational pull from other solar system bodies is very minor on PLATO. That said, keeping a spacecraft in L2 is not easy - there is nothing to "orbit".
And when the reaction wheels get saturated they have to expend propellant to let them spin down. It is a fascinating mechanism.
Here is the Wikipedia about Lagrange Points (L2 is one of these): https://en.m.wikipedia.org/wiki/Lagrange_point
The orbital corrections are minimized at L2, because of the relative distance of the moon and other planets vs size. But that is what is accounted for in the corrections.
James Webb Telescope is at Sun-Earth L2.
How far away PLATO will be from the James Webb Space Telescope? How big is the L2 Lagrange point? (i.e., how closely do you need to be for an orbit around L2 to be practical?)
> How big is the L2 Lagrange point? (i.e., how closely do you need to be for an orbit around L2 to be practical?)
The L2 point doesn't really have size, and even its location isn't stable. It's a mathematical point, and when we say "orbit around L2" then that is not fully true either. The spacecraft are on what's called "halo orbit" - maybe imagine balancing a steel ball (like from a bearing) on a bottle that's sideways, it's probably easier to roll and balance the ball lenghtways of the bottle, than on rolling it sideways. The best analogy I could come up with. You don't want to be too close to the L2 point, as then the orbit would be very short and less stable, think of it as having a smaller bottle - probably harder to balance the steel ball on a smaller bottle than a big one.
> How far away PLATO will be from the James Webb Space Telescope? Probably on the magnitude of hundreds of thousands of kms on average. Interesting question though, hopefully they won't get too close :D
Let me remind you guys that "just 20 light years" = roughly 200 trillion kms. At the speed of voyager 1, it takes roughly 1600 yrs to travel 1 trillion kms. 200 trillion kms would take 320,000 years to reach there. Even if you increased the speed of voyager 1 by 10 times, it would still take 32000 years to reach. We really need to up the speed by a factor of 10000 before we can get anywhere close to human lifetime achievable travel times.
Accounting for acceleration and deceleration seems like an unspoken obstacle in your timeline. How can a human comfortably accelerate or decelerate at a rate greater than 9.8m/s^2 for long periods of time? “Hey guys, we will need you to pull 9Gs for the next seventy years as your ship slows down to enter a stable orbit”
Accelerating consistently at 1G (and then -1G for the second half), should take 6 years of proper time (from the perspective of the traveller) to get there.
Yea, actually the problem is not at all that we’d need too much acceleration for the human body. Accelerating at 1g for a couple years gets you to preposterous speeds (and we don’t even need any artificial gravity nonsense!). The problem is that accelerating at 1g for years would require a ridiculous amount of energy.
In his 1958 juvenile novel Have Spacesuit, Will Travel (I read it years later as a tween), Robert A. Heinlein described this as a "skew-flip maneuver" that would get someone from Earth to Pluto in five days at 8G (!). And apparently E.E. "Doc" Smith described it even earlier.
https://en.wikipedia.org/wiki/Have_Space_Suit%E2%80%94Will_T...
https://scifi.stackexchange.com/questions/261753/what-was-th...
And because faster acceleration only gives you square-root returns, a leisurely 1G trip going the same distance is still over in 14 days.
Huh. I've heard lots of science fiction ideas for artificial gravity, usually starting with rotating space stations.
I never heard of anything so obviously straightforward as that, though. Surely impractical, but good to know!
You should read the The Expanse books (or watch the show).
Don't they use magnetic boots in the Expanse (at least in the show)?
Only when not under burn.
I don't think we'll be sending humans on these kinds of missions. We'll be sending AI systems (ship, bots, etc.) and then waiting millennia for them to report back.
It's conceivable that we could send the seeds of humanity and other terrestrial life — along with AI systems capable of raising it, terraforming the planet as necessary, and building a society.
We might not ever travel there or receive guests from New Earth any time in the foreseeable future, but it's fun to imagine that one day we could have a colony of distant pen pals separated by only 20 years of latency.
Under current financial and incentive system this will not going to happen unfortunately.
You just need to be constantly accelerating to hit very high speeds very quickly. You don’t need to pull 9Gs throughout.
I have a feeling that when we figure this out, the forces of acceleration and deceleration will no longer be a problem.
Or alternatively, we make Alcubierre spacecraft work, or we move our whole planet system.
All entirely plausible approaches :D
Even the fastest spacecraft ever made (the parker solar probe) "only" went at 692000kph. So 1,000,000,000,000/692,000 = 1,445,086 hours, or 164 years.
How fast could a ship get going with a RTG powered ion engine like AEPS? Rough back of the envelope figures come out to 100 years to cover 1 light year, or a few thousand to reach 20 ly out, which is... nothing like science fiction books but not impossible either.
> before we can get anywhere close to human lifetime achievable travel times.
Humans are an intermediate step. We are not the final shape of earth-origin intelligence.
Why would we continue to fill these bodies when we develop the tech to no longer be so limited? Constrained to the parameters of our gravity well and to short lifespans without backup?
Or maybe we just get replaced outright.
Or, the worst outcome, everything from this planet dies without ever having left.
You can’t develop tech to move intoto a computer. Although it’s a good book idea.
A kool-aid style cult where they convince their followers they will be “uploaded” once they hand over all their possessions. Then they just get shot in the head.
AI might do it, but I wouldn’t count that as us going there.
You're inventing requirements. This doesn't require that any of us live or achieve immortality.
Realistically if we perish and there is no comparable conscious life then no one can even care whether a bunch of machines we spawned to assist us continues to exist.
Thinking 'it is good' is a product of your consciousness. When there is no one to judge then there is no 'good'.
A universe full of p-zombies
If you haven't, read "blindsight" by Peter Watts
+1. Aliens and vampires in the same book. And really far-out ideas about cognition and biochemistry, well-grounded in science.
It's murky concept though, so I wouldn't bet on mind uploading in our lifetime.
Some fairly fundamental things need to be answered first. Things like how does consciousness and the sense of self arise.
Naively, if you think that you are just a program that runs on a bunch of neurons in your brains, and that this program can be uploaded to a computer, you are still left with a very annoying problem: you upload a copy, and leave the original running in your squishy brain. So what then? Do you kill the original? But that involves killing a living and breathing human being. Do you wait until it dies naturally? That's still not a good answer, because you have to die so that a copy of you can continue existing.
So until we figure how to actually "teleport" our consciousness to some other host, we are in a pickle. And there's absolutely no evidence that we'll ever be able to do this teleportation. What if we never figure out the physics to do this?
Edit: I suppose you could sidestep this by generating fully digital consciousnesses that mimic what a human brain does. So a fully digital human. Assuming we can brute-force simulate a real human brain, this should be at least physically possible (as opposed to teleportation), but this still raises philosophical questions. What you are generating then aren't human beings, but conscious AI. You could argue that the human race would eventually be supplanted by immortal AI that are no longer bound by biology, but I'd argue that this isn't an evolution of the human race, rather a completely new life form (if you can call it that), which has nothing to do with humans except that we created it.
You're imagining a future that is a continuation of our lives here and that is kind to currently living humans. But this is just inventing requirements.
Imagine none of what you've presumed is necessary is even a design objective. Maybe it is, but probably it's too difficult and uneconomical. These capabilities could be built without ever enabling any of us to live or achieve immortality.
Those hypothetical digital beings could be human-like, maybe exact simulations, or perhaps totally different. They could be benevolent, or perhaps not. We might come to a conclusion that it's no longer ethical to have biological humans. Or maybe we're forced into that outcome.
Who knows. This is all wild postulation. But one thing that might happen is runaway growth and a deviation from a world we're familiar with.
I’ve never understood the idea that humans should be doing space exploration. Especially given the proof that robots and machines are demonstrably better and more suitable for these kind of tasks by such a degree that they dominate off-planet sensors-effector combinations.
Making space exploration comfortable for humans instead of creating TARS like intelligent machines (possible in our lifetimes imo) foundationally limits and constrains the ability and scale of exploration.
Seems entirely egoistic and anthropocentric. Is there any alternative reason - other than stated - as to why humans should be considered the best candidates for these tasks?
Because they want to. We see mountain, we climb it. Space is no different.
I wonder if space exploration will turn out to be no different than mountain climbing. There's nothing useful on the mountain, we can't live there, it's purely exploration, sport, and a feeling of achievement.
There's an entire universe out there, we will definitely find some useful stuff.
We may never solve the distance problem, for example, so all we may end up with is telescope images of the useful stuff.
I'm not saying we shouldn't try, by the way - we definitely should.
You clearly don't do mountaineering :)
By far the most motivating part of high dangerous mountains is the internal journey of climbers to have confidence in your own skills and training to overcome any obstacle that can happen. Then facing an unpredictable challenges, trusting your teammates if you are not solo, overcome them or knowing when to retreat to safety.
Facing semi-continuous fear of death, not getting hampered it but calmly assessing it and acting accordingly is a great skill for any aspect of life. Overcoming oneself mentally, pushing and redefining our own limits (normal folks have them mentally set very low compared to actual threshold) is the gist of it.
All this and much more while being mentally degraded to 10-20% of capacity at sea level. in environment where 1 mistake can be easily the last one. Physical capacity is also greatly reduced, and you climb very steeply or almost vertically, with 10-20kg backpack, sometimes more. Doing this even for weeks without break. Summit push can be easily 48-72h 100% effort without a sip of water, any food nor sleep, after all I've written. I wouldn't even call this 'sport', you don't call early Antarctic expeditions a sport, do you.
I don't see why almost all of this and much more shouldn't be present in space exploration, just environment will be a bit different (but views on myriads of stars remain).
Humans generally do things out of their own self interest (which for a lot of people includes improving the living conditions of their descendants). So, if humans aren’t going to colonize space, we’ll either need somebody who… just sort of likes colonizing space with robots? Like as a hobby I guess?
Or maybe we’ll have robots at some point capable of working in their own self-interest.
If these robots find a good target and make it habitable, then you would still need to send humans at some point, right? But then you sort of wasted all these thousands of years by doing robots first, you might as well send humans too.
Yes, but that’s only a few hours away through hyperspace !
The existence of the Super-earth was not directly observed, but was instead inferred by the gravitational lensing of all the democracy[0] being spread in a sphere around the planet.
[0] https://helldivers.fandom.com/wiki/Super_Earth
We know that, due to the lack of observable galactic civilizations, if there is a Space War For Democracy, it is a Shadow War [0]. Perhaps with one exception [1].
[0] https://babylon5.fandom.com/wiki/Shadow_War_(disambiguation) [1] https://en.m.wikipedia.org/wiki/Tabby%27s_Star
It's not in the habitable zone 100% of the time because of its eccentric orbit.
in Vernor Vinge's novel A Deepness in the Sky the alien planet freezes for part of the year and the intelligent aliens have evolved to survive being frozen and thawed. One group develops technology to say unfrozen while their enemies are frozen and this gives them a huge advantage.
Great book and I highly recommend it. Also has concepts of realistic mind control that is VERY creepy and the ultimate in distributed computing based on smart dust.
This general idea is explored in many other pieces of science fiction literature, but it has also recently been visualized in https://en.wikipedia.org/wiki/3_Body_Problem_(TV_series)
So kind of like living in Minnesota?
Ya' know, Oly was very happy to find his farm was in Iowa, rather than Minnesota. When his friend Sven asked him why, given that taxes were higher in Iowa, Oly replied "Vell, now I don't have to put up vith those lousy Minnesota vinters no more!"
How do they evolve when they are frozen part the year before evolution?
Life in that planet evolved to essentially hibernate during their long winter. Presumably the processes that resulted in the very earliest life forms happened countless times until some surfaced that had that feature.
> Its distance from its star changes significantly, causing the planet to move from the outer edge of the habitable zone to the inner edge throughout its year
Too bad that the year is relatively short. If it were hundreds of Earth years that could be like Helliconia https://en.m.wikipedia.org/wiki/Helliconia
It's not in our habitable zone.
Life on such a planet seems likely to hibernate just like some Earth life already does.
> It's not in our habitable zone.
The habitable zone is defined as the area around a star where liquid water could be found, there is no "our" habitable zone and "their" habitable zone.
Parts of our own Earth aren't in the habitable zone, by that definition. Even here we get big surprises - undersea vents were unexpected oases, microbes miles deep underground, microbes living in boiling water in Yellowstone...
Not all life in the universe may require liquid water, nor require it 24/7. In our own solar system, some planetoids outside our supposed habitable zone likely have some liquid water - Europa and Enceladus, for example.
> Parts of our own Earth aren't in the habitable zone, by that definition.
What parts would that be? Even the polar caps have huge liquid water oceans underneath. Unless you’re talking about the mantle or molten core, there are no uninhabitable areas on earth as per astrobiology (not even miles underground).
> Not all life in the universe may require liquid water, nor require it 24/7.
You might as well be talking about leprechauns and unicorns and Horta. Water is the universal solvent and has at least five unique properties that are as critical to life as carbon’s ability to form four chemical bonds.
You’re correct that moons experiencing tidal heating can contain liquid water, but that’s irrelevant to a planet. The habitable zone is specifically talking about planets (rocky ones at that), not any arbitrary satellite. It’s a term of art in astronomy, not a colloquialism.
> Unless you’re talking about the mantle or molten core, there are no uninhabitable areas on earth as per astrobiology (not even miles underground).
We've found microbes that can survive at 120 Celsius, -25 Celsius, very high and very low pH, large amounts of ionizing radiation, intense pressures, etc. Habitability is a wide range encompasing scenarios not conducive to liquid water.
> Water is the universal solvent and has at least five unique properties that are as critical to life as carbon’s ability to form four chemical bonds.
None of that rules out life on other chemistries. It makes water+carbon-based life the most likely scenario on planets with liquid water, but hardly rules out other potential biologies.
> You’re correct that moons experiencing tidal heating can contain liquid water, but that’s irrelevant to a planet. The habitable zone is specifically talking about planets (rocky ones at that), not any arbitrary satellite.
But we should absolutely be looking at planet-sized moons with potentially habitable conditions, which we believe to be quite common. They are, after all, more common than the single "habitable zone" planet even within our own system.
>None of that rules out life on other chemistries
Is the upshot of this observation supposed to be that PLATO should change its plans and direct its telescope in a different direction because it has more promising places to look than the habitable zones around stars?
If not, and if you can understand why it's prioritizing that, then why do you take this definition of habitability to be tantamount to denying the possibility of discovering other forms of life? For those possibilities to be relevant to a research program, they need to be motivated by something more than "gee, hey, you never know."
So it's not for lack of reflection on those possibilities that we arrive at this operative definition of habitability. There are pertinent reasons for moving forward with this definition that don't amount to denying other boutique possibilities. Construing it that way I think is just an uncharitable interpretation.
Dude, just read the Wikipedia article: https://en.wikipedia.org/wiki/Hypothetical_types_of_biochemi...
It’s not impossible, but we’ve got a ton of evidence why it’s extremely unlikely. It’s a long list including stuff like possible quantum transition states enabling biochemistry, reactivity with oxygen (the third most abundant element), and spectroscopic transparency. It’s an active area of research that keeps coming up with dead ends.
Ammonia and methane are the best candidates but those would only be possible at low temperatures that preclude lots of other reactions.
The Wikipedia article supports my point - plenty of smart folks think it's at least plausible for alternative chemistries to work.
An ammonia-based life form at our stage of exploration is probably gonna scoff at the idea of scaldingly hot liquid water as a basis for life, too.
> It’s an active area of research that keeps coming up with dead ends.
So's SETI so far, but I'm not willing to conclude extraterrestrial life is impossible just yet.
And none of those smart people have come up with any experimental evidence that it’s actually possible. No equivalent to amino acids or nucleotides or saccharides or… the list goes on.
I’m not talking about SETI, I’m talking about basic chemistry experiments. There are tons of experiments that can spontaneously form amino acids and nucleotides, even way outside the parameters normally considered habitable.
That's similarly true for carbon-based life; abiogenesis remains a hypothesis in search of concrete evidence.
There is tons of concrete evidence, you’re just ignorant of it. Start with Stanley Miller’s seminal 1953 paper “Production of Amino Acids Under Possible Primitive Earth Conditions” and go from there. There’s been a lot of work on the topic since then, several of which have made it to the HN front page.
I'm aware of the Miller-Urey experiment.
It's only one piece of the puzzle, and we're aided significantly in it by knowing what the results are supposed to look like.
We absolutely know what it’s supposed to look like: monomers. Monomers that can form polymers.
The specific chemical details are irrelevant. We have no evidence of other monomers that could enable non-water based life.
We find polymers outside of Earth-like conditions.
https://en.wikipedia.org/wiki/Hemoglycin
> Hemoglycin (previously termed hemolithin) is a space polymer that is the first polymer of _amino acids_ found in meteorites.
I’m done, have a great day! (Monomers)
Edit: My apologies for being dismissive. I’d like to get into the specifics of why amino acids (amino and carboxylic groups specifically) are special, and interesting exceptions like hydroxy and alpha-hydroxy acids, but I’ve got to get to work and I could spend an entire year explaining the nuances. The deeper you get into the details, the more the anthropic principle rears its ugly head.
> ammonia-based life form at our stage of exploration is probably gonna scoff at the idea of scaldingly hot liquid water
Ammonia-based life exists within water habitable zones; Mars is within our Sun’s conservative habitable zone [1]. (Also, “ammonia boils at 98°C instead of –33°C” at “60 atm, for example, which is below the pressures available on Jupiter or Venus,” meaning “ammonia-based life need not necessarily be low-temperature” [2].)
One reason to suspect ammonia-based life is rarer than carbon-based life is the universe contains a fifth of the nitrogen that it does carbon [3]. (This is why silicon-based life is also almost written off.)
[1] https://en.m.wikipedia.org/wiki/Habitable_zone
[2] https://www.daviddarling.info/encyclopedia/A/ammonialife.htm...
[3] https://en.m.wikipedia.org/wiki/Abundance_of_the_chemical_el...
How is it clear at all that extraterrestrial life is more likely carbon based than not. Is there any evidence other than it's the only one we know?
PBS Space Time has a very good & informative episode covering this. I'll try to dig it up.
Most elements are missing some key properties that carbon has.
Silicon is the next most-likely element, but it's still missing out on a few properties that carbon has.
Here:
https://www.pbs.org/video/what-if-alien-life-were-silcon-bas...
Or on YouTube:
https://www.youtube.com/watch?v=469chceiiUQ
Do any of those zones actually have life?
The two examples you gave... Include liquid water.
As far as I know there is no life native to the coldest parts of the earth that have no liquid water.
It is entirely possible there is some other form of life that does not require liquid water, but we have yet to discover it.
> The two examples you gave... Include liquid water.
This specific planet spends half its orbit in said zone. Here on Earth, we have creatures like https://en.wikipedia.org/wiki/Mudskipper that can survive severe dry spells, and fish that can happily freeze sold in ice for months.
Europa spends zero time in our solar system's "habitable zone", but because of its conditions, may still possess large amounts of liquid water. It's a perfect example of why the "zone" may be overly narrowly defined, even for Earth-like water-dependent life.
> It is entirely possible there is some other form of life that does not require liquid water, but we have yet to discover it.
And we certainly won't if we only look in Earth-defined "habitable" zones.
You seem to be deliberately trying to pervert the definition of habitable zone.
Just because there are regions on a planet in the habitable zone that contains ice does not mean it is not in the habitable zone. If it were further out beyond the habitable zone, there would be no liquid water at the surface.
To quote my friend Andy Dufresne, "How can you be so obtuse?...Is it deliberate?"
> You seem to be deliberately trying to pervert the definition of habitable zone.
They're fine. Some people here are trying to overextend the definition and it's good to push back.
The habitable zone is about surface water. Pointing out that parts of the earth lack surface water for extended periods is a really good analogy to a planet that drifts in and out of the habitable zone.
> You seem to be deliberately trying to pervert the definition of habitable zone.
No, I'm saying an Earth-life centric metric is a bit of an odd choice when evaluating extrasolar planets.
It's like an African elephant declaring Norway uninhabitable.
Earth is the only environment in which we've found life, so it makes sense to first focus on other Earth-like planets. Your point is not without merit but taken to the extreme it would be like sending exploratory teams to the Mariana Trench to look for un-contacted human tribes.
We have incontrovertible evidence that water + carbon + time sometimes equals life. We have no evidence of any other non-carbon or non-water chemistries resulting in life so why wouldn't we focus on locations potentially rich in water and carbon first?
The first exoplanet detection was in 1992; in my lifetime, "there are no planets outside our solar system" was roughly as supportable as "there is no life outside our solar system" is today.
Here on Earth, we can barely decide if viruses are life or not, and discover new things within our own bodies pretty regularly, despite... a lot of direct access to them. (Example: https://www.science.org/content/article/it-s-insane-new-viru...)
We should be casting a pretty wide net.
You seem to be talking past everyone else in this thread because nobody has disputed a single thing you've said however you're ignoring (perhaps unintentionally) the basic statistical reality that if we focus on potentially water- and carbon-rich environments we are as a matter of course more likely to find life sooner.
But the "basic statistical reality" is also "there are a lot more known/accessible planets outside of the zone in which liquid water exists naturally on the surface", which leads to a quantity vs quality consideration for which we don't have enough information to decide right now.
Yes but "we don't have enough to decide" means you have to lean on the single data point you have, not completely ignore it and just try to look everywhere all at once. You have to focus your finite resources and "just pick something" isn't a reasonable path when there's more things to investigate than we could do in 10 lifetimes.
The correct scientific approach to a sample size of one tends to be "not enough information to make a decision".
Lets start our search for helium-based life forms immediately!
Or maybe we start with what we know (carbon-based), and keep our minds open to other possibilities. Like we do now.
> Or maybe we start with what we know (carbon-based)
But we know more than one thing. One of those things is the Fermi paradox - that the universe should statistically be full of evidence of life, and yet we struggle to find it. That may be evidence we're making the wrong assumptions.
> keep our minds open to other possibilities...
Yes, and I'd argue that means including scenarios like Jupiter's moons in our search. (As a bonus, Jupiter-style planets, being larger and far from the star, are substantially easier to find.)
Like you said, the first exoplanet was detected in your lifetime.
We haven't even had the chance to fail yet, the Fermi paradox is not yet in play when we're considering essentially our first move. To extend an analogy from further up thread, it'd be like looking in the Mariana Trench for un-contacted human tribes after taking a quick glance around the neighborhood and deciding there's nothing else to be found anywhere else.
Look up "informative vs uninformative prior".
There's a meaningful operative definition and you're muddying the waters over that definition on the grounds that, hey, who knows, maybe it's different somewhere in some way.
I just think you're confused if you think that observing a specific definition of habitable zone is tantamount to a specific denial of that possibility.
I'm not confused by its definition, I just dislike the use of the term. It leads to significant confusion in laypeople - "they found a habitable planet!" is something I've heard breathlessly repeated multiple times, and "but Earth is so perfectly placed, it can't be by chance!" used as an argument for creationism.
Given the mass of the planet, if there's a lot of water it's entirely possible there could be oceans which stay warm due to a hot core.
Regardless of the official definition, the word “habitable” is highly subjective. Extremophiles like tardigrades can survive being frozen and/or completely dehydrated. A planet with an eccentric orbit like this one could hypothetically support species capable of entering some form of extreme hibernation during part of their year.
>the word “habitable” is highly subjective.
Sure, but not in the context of "habitable zone" which is a specific term of art in astrobiology.
> specific term of art...
And that's fine, but when communicating outside the speciality, I'd really like to see some other term used.
https://www.cjonline.com/story/news/politics/government/2025... for example says "Kansas tuberculosis outbreak is now America's largest in recorded history", where "recorded history" is apparently the CDC's "term of art" for "since 1950", which isn't what a layperson hears.
>And that's fine, but when communicating outside the speciality, [...]"
The IAC, where this article is from, is the Instituto de Astrofísica de Canarias (literally the "Institute of Astrophysics")
That's about as far into the specialty as you can get.
The IAC is communicating outside the speciality here, via a press release.
That's why the article's breadcrumbs say "Home > Outreach > News".
We saw the same issue during COVID - scientists talking to the general public often talk like scientists instead of science communicators, and that causes people to misunderstand. Fauci's "no evidence" (yet) masking prevents disease incorrectly becomes evidence masking can't prevent disease.
Not many uninterested laypeople are going to be browsing the IAC website for astrophysics news. People that are interested should probably familiarize themselves with the terminology commonly used in astrophysics.
Once it makes its way to PBS Space Time, sure, maybe you avoid terms of art. Or explain the particular definition when it is first introduced.
That's just my opinion anyways. I always try to familiarize myself with the common terms of art when learning about a new discipline.
> Not many uninterested laypeople are going to be browsing the IAC website for astrophysics news.
But they will get linked to it, or read articles by reporters using it as a source without enough domain knowledge to make the distinction. I, after all, didn't seek this out - it just popped up on the HN home page.
> What seems weird to me is to be interested in a discipline, seek out news and conversation about it (from university press releases!) but then reject and/or argue about any terms of art that are established within that discipline.
I think science communication, post-COVID, needs to take a serious look at how to better explain things to the public. "Habitable zone" is simply one example of it.
I edited part of that out, because I actually do broadly agree with you regarding science communication, and realized my comment was a bit stronger than I intended. Looks like you were quick on the quote!
However, I think there's some serious slack to cut when you're viewing an article on the Institute of Astrophysics website, compared to reading Fox/CBS/whatever.
Edit: In my re-reading of the article, I see they define it! I'm no longer sure what all this back and forth is even about. "This orbit places it within the habitable zone of the system, _meaning it is at the right distance from its star to sustain liquid water on its surface_" Do you want them to not use the term even when they define the term?
> Do you want them to not use the term even when they define the term?
Yes, I do. I think it's a needlessly confusing term to use in stuff intended for public consumption.
For a similar example of the issue, I often get radiology reports in my healthcare provider's portal. My dad is a radiologist and they're still quite scary/bewildering to read - they frequently use various terms of art for "looks fine and normal" that sound terrifying.
That was all fine when the intended audience was other doctors, but these days I can pull them up myself. I at least know enough to not freak out and ask my dad; many don't.
I don't want to see NBC/BBC/NYT articles using the term, and that means being careful with the sources from which they receive their info.
While it's possible for conditions for life to emerge or sustain itself to be present beyond the habitable zone (e.g. there's likely a subsurface ocean orbiting the farthest plant from the Sun on Triton), afawk it is more probable that life forms in the habitable zone. That is the only one we have a data point for.
A sample size of one tells us it it possible, but nothing about what’s most likely.
Well, we also know where we haven't found signs of life. So from that perspective we have more data.
>Regardless of the official definition, the word “habitable” is highly subjective
Well, one constructive way to take it out of the realm of subjectivity is to put forward a specific definition.
The terminology was probably chosen specifically to be somewhat clickbait, so it's probably not worth picking apart the words "habitable zone".
The core idea really boils (heh) down to water, _i.e._ the "universal solvent". You can certainly argue that liquid water may not be necessary for life, but it's hard to argue that water's presence isn't a decent prior for potential life.
But directly detecting liquid water in extrasolar planets is _hard_. So we do the next best thing and try to use whatever indirect signals we got. We know that liquid water can only exist within some range of temperatures and pressures. So let's just start with temperature.
What things can affect the surface temperature of a planet? Amount of energy received from the parent star (i.e. stellar irradiance), geothermal heating, tidal forces between a moon and planet, and probably many others. Stellar energy stands out as being the biggest contributor of energy and, fortunately, the easiest one to measure.
Of course, you could have localized sources of favorable conditions, like thermal vents or whatever, but those kinds of things are _way_ beyond our ability to detect with current tech.
So, we've narrowed down our focus to _one big contributing factor for potential life_, the amount of energy received from a planet's host star. But how can we relate energy to temperature? This is effectively where all the physics and astronomy come in via thermodynamics, orbital mechanics, and stellar physics.
Suffice it to say that all the effects combine to give a range of possible orbital radii and planet sizes where liquid water has a good chance of existing on the planteary surface.
This range of radii and planet sizes is the concept that matters. The name for this idea is "habitable zone", which suggests why we might care, compared to the more precise "orbital and planetary mass parameters favorable to liquid water formation at average planetary surface".
Reminds me of the planet inhabited by Arachna spider species in Vinge's A Deepness in the sky.
This kind of resource variability seems likely to favor the development of intelligence, so there’s that.
But I m sure we will find that the planet has issues that make complex life unlikely, just on a statistical basis.
Simple life seems increasingly likely to propagate through panspermia, based on what we find deep inside the crust of our planet. Life forms that feed off of radioactive decay especially seem promising for panspermia.
I wouldn’t be surprised at all if we discovered that for habitable zone, earth-like planets , the presence of simple life forms deep inside the crust turns out to be the rule rather than the exception, at least in our corner of the galaxy.
Highly recommend listening to In our Times (BBC) episode "The Habitability of Planets" that was aired last month.
https://www.bbc.co.uk/programmes/m0025vvd
My napkin math says the surface gravity would be around 30 m/s2.
I'm not looking forward to a visit. Maybe it has a large moon like Earth. If it is in the same proportion as ours, the moon might even be friendly to humans.
Habitable exomoons is a cool idea [1]. "Scientists estimate that there are as many habitable exomoons as habitable exoplanets"
[1] https://en.wikipedia.org/wiki/Habitability_of_natural_satell...
I see all those big gas giants in the habitable zone and always imagine the kind of civilisation that can emerge from that scenario.
Eccentric orbit.
Too cold is one thing, but too hot I suspect is harder to handle.
Not sure how "artist's impression" the graphic in the article is, but it shows the innermost orbit being just on the edge.
Given we have ice on Mercury right around here, and the fact that I have to pressure can stuff like garlic because boiling won't kill spores, probably not a dealbreaker. https://nssdc.gsfc.nasa.gov/planetary/ice/ice_mercury.html
If a "humanoid" from this planet visited Earth with 1/6 of their normal gravity, would they be a super athlete, or barely functional?
Ever pick up what you thought was gonna be a really heavy box and it turned out to be empty, and got briefly thrown off-balance? I'd imagine that, but for everything.
Oh good, so it's not just me that happened to!
The moons gravity is 1/6 of the Earths. So looking at our moon visitors performance, a super earth visitor would probably be great at high jump but pretty shaky at anything else.
I wonder if jumping even makes sense at 6x gravity... maybe they would never have learned how to jump at all and always keep some limbs in contact with the ground.
Or if "humanoid" even makes sense. Something snake like that can spread out the pressure along a longer surface might be better. Or at least something with more than two legs.
What body shape would creatures living at six times the gravity even have? Would they be able to jump? Would they have a skeleton as we know it?
I would almost go looking at deep sea creatures that have to deal with extreme pressures on earth.
They might have to be entirely aquatic at that point or perhaps have some very exotic skeletal structure that can support their weight. Perhaps ball shaped beings who roll around instead of any sort of walking? I'm unsure how would they deal with a small incline.
Weight lifters are able to lift 6x their body weights, but it's not a sort of load that we could profitably exist under long term. We'd need to have extremely thick limbs and at some point that won't help either because of the cross-section vs. weight scaling law. It's also a sort of weight where any kind of leverage against a joint will generate massive forces. E.g. try catching a 50kg falling weight, you are likely to dislocate your joints and/or break some bones. And yet 1/6 of that is entirely manageable.
If intelligent life exists on a superearth it would be trapped there because rockets wouldn't be able to reach orbit. In fact 1.4g seems to be the max that chemical rockets can escape. Maybe they could built an electromagnetic launcher on top of a absolutely huge ramp.
Or they would be forced to figure out technology that we would consider science-fiction, assuming it's possible. To consider our tech as the pinnacle is the wrong approach, I think.
Perhaps we've had it too easy here - moderate climate, oil as an easy fuel source, and gravity that isn't too oppressive. I wonder what technology would arise in a more difficult environment, such as this superearth.
Ironically I think you’d be more likely to go to space on such a planet. Imagine being barely able to jump, let alone fly. You would want to leave more than anything. It would be like a space race, against the universe.
I’m imagining some sort of mega cannon or railgun as a propulsion method to fling them off the planet.
Nuclear thermal rockets would also be an option.
I asked a physicist friend about this. At 6x mass, it would only be 6x the gravity if it was the same size as Earth. Depending on the density, the gravity could actually be weaker than Earth!
Yeah, not having the radius/diameter of the planet mentioned really hurts understanding the effect of that mass. However, I doubt it is like Saturn where it could float in water.
https://www.aanda.org/articles/aa/full_html/2025/01/aa51769-... ("Revisiting the multi-planetary system of the nearby star HD 20794")
I'm sure the aliens reading that are saying "Thank god! They aren't coming here." :-)
But on a more serious note, this is some great science. I am super impressed by how sensitive the instruments need to be to chart the fluctuations due to mass here at 20 light years. I'm always on the fence about whether or not we should focus a beam of RF with some modulation on it in their direction, on the one hand it would say "hello! we see you!" on the other that might not be a good idea.
Just 20 light years away (As a normie I giggled a little).
Helldivers predicted this
Arrowheads marketing team moving heaven and Super-Earth for the 1-year anniversary of the release on February 8th?
FOR SUPER EARTH!!!
My life for Super Earth!
?
Humans live on a planet called 'Super Earth' in that game
The Raleigh criteria for 1km resolution at 20ly requires an interferometer with a baseline of 120,000km. That’s about a third of the way to The Moon or 10x the diameter for The Earth.
How far away is such technology?
For 1000km resolution the requirement is three orders of magnitude smaller, or ~120km. Could such a device be terrestrial?
Super Earths are a one-way trip right? If you land, you can never take off again due to the tyranny of the rocket equation.
Barring science fiction, of course.
Depends on the radius, as I understand it. It could have more or less gravity depending on that, but we don't know what the radius of this planet is yet.
Wolfram Alpha has a good calculator if you want to play around with this [0]
[0] https://www.wolframalpha.com/input?i=surface+gravity+calcula...
Great! Let´s go there, kill all life and destroy everything, like we are doing on our own planet! Just imagine how RICH we can get!
Is there a way to estimate gravity on remote planets? Wouldn't the mass of this body, which is six times larger than Earth rule out the habitability?
Initially thought Infrastructure As Code achieved this discovery.
Well, the planet is terraformed
And only 20 light-years away...
That's only one generation that would need to be raised on a ship
If we managed to build the ship and if we managed to get it to same speed as our fastest space probe, it would take around 35000 years.
It might as well be a billion. Humans in our current form can't survive interstellar travel. We would need a far more durable substrate.
At 99% the speed of light it will take the traveler less than three years, while 20 years passes on earth. If they then turn around they will return to earth, they will arrive aged 6 years while 40 years have passed on earth. You can come back younger than your children.
Which then makes for an interesting moral or ethical dilemma: is it ok to embark on such a mission after having children, knowing that they will live half a lifetime without you and, assuming you left before the age of 34, will be older than you when you get back.
Generational migration can be done.
Since each star is different, it seems like the inner and outer limits of each habitable zone would also be different for various stars. Is it just the mass of the star that determines this, or are there other factors?
Only 20 lightyears sounds good, and the elliptical orbit within the habitable bounds sounds also good, comparable to our summer-winter shifts. Now they need to detect water
Summer and winter on Earth isn't due to elliptic orbit, but the tilt of the planet. This planets orbit takes it both inside and outside the habitable zone on each orbit. That's very very bad. Going from Mars-like to Earth-like to Venus-like every year.
Not very bad per se. It would be summer and winter for the whole planet, in longer cycles. It didn't hurt the development of advanced civilizations on earth at all. You have pressure to adapt.
My second, more intelligent, rational take: goodness, that's exciting! I can't wait to see more research as it follows.
My first, drowned-in-doom-news take: can I move there? Immediately?
The only thing more exhausting than people acting like an election instantly makes everything great and the world is now going to be amazing is the people acting like it's literally the end of the world.
You will not be substantially better or worse off a half-decade from now than you would have been in a slightly different circumstance.
Tell that to someone who lived in Germany in 1933.
Honestly a really bad take given the current environment. This is the not the thread for it but I'll point out that just today funds families around the USA and world require to live were pulled out from underneath them, regardless of law. I have a child who depends on those funds so it impacts me greatly, and I don't know if that child will be around long enough without funds for her care.
So please do not minimize what people are going through, it may not impact _you_, but many people are negatively impacted by the insurrectionist taking over the USA.
I invite you to stay on Earth.
Balance compassion for yourself and others. Finding the balance is really hard, maybe impossible to do perfectly, so you have to try constantly. When you get close, I think you'll find that negativity evaporates in yourself in a way that's infectious to those near by you. Take care.
I pray we get star treck replicators.
we're a long way from there, but 3d printers are the very first step to getting there
I love that the planet is similar to Earth in mass and orbital time.
Feels like our older cousin from just 20Ly away
lets have a look https://en.wikipedia.org/wiki/Solar_gravitational_lens
I’m sure we will see a sign that says “go away stupid humans”
> HD 20794, a star with a slightly lower mass than the Sun and located just 20 light-years away
I'd prefer to hear about interstallar travel news rather than DeepSeek ones :-) The pale-blue-dot is really generating anxiety :-/
Check out https://www.centauri-dreams.org/, it's a blog dedicated to interstellar travel. It's on hiatus at the moment, but there are plenty of back articles to read!
However, I recommend you figure out how to reduce your anxiety, because after reading it for a while it will become clear that interstellar travel isn't happening any time in the foreseeable future. Fortunately, I don't think that a species that flourishes from the hot tropics to the freezing arctic is likely to be in much existential danger from climate change, and even less from the volatile vagaries of politics. (Climate change might bring very substantial changes, but escaping off-planet isn't going to be less change)
Well, let's go!
Ok, when's the next flight out?
"the new planet ... tak[es] 647 days to complete an orbit around its star, 40 days less than Mars. This orbit places it within the habitable zone of the system, meaning it is at the right distance from its star to sustain liquid water on its surface"
1. That orbit make it really cold relative to Earth - like Mars is.
2. It doesn't say that the planet has a human-breathable atmosphere; it might, but it might not - like Mars.
Also,
3. Gravity force is gMm/R^2 right? Let's say same density as earth, and that density is uniform. Now, the mass relates to the radius by R^3, so the gravity force will be higher by 6^{1/3}, or about 1.817x higher than Earth.
So, would you say this is a habitable planet? It's kind of a stretch.
So can we now have a trio of ulra large optical telescopes, flying in an ultra high resolution formation, used to create images useing optical interferometry, now. Now? Want! And if the international astronomic comunity drags there feet , advocating for more "science" missions, and getting proof of exo habbitats befor they can look for them, tenures safe, then lets defund the whole mess, and build telescopes at scale, get optical data, and THEN they can theorise in they very own arm chairs at home, about all the anomalies they want.
so... not the Barry Diller IAC that owns all the dating apps?
cool, ultimately meaningless but cool.
I don't think this is a good take. Discovery & science are inherently meaningful even if the applications are not immediately felt. Nuclear magnetic resonance (NMR) was discovered in 1938, but there was no obvious applicability of it to everyday life. In 1971, 33 years later, Paul Lauterbur used it to develop the first MRI
Superearth means super gravity too.
"Intersecting" the habitable zone isn't the same as "within," I find it curious that discussion of the ramifications are far down, it seems pretty salient to me...
The idea of an ecosystem hence culture for which a fundamental cycle is a year of fallow hibernation followed by a year of fertile plenty is quite compelling as a scifi trope though.
Me I'd name the planet Persephone for this reason.
Does it have Super-humans?
Just a reminder that if, for some reason, we discover technological civilization on that planet, it's very, very bad news for us as a species.
I'm talking about the Fermi Paradox. Basically, given all the stars we can see and that we see planetary systems around virtually every star we look at, then a decent portion of them should have rocky planets in the habitable zone. A portion of those should have the conditions conducive to life. A certain percentage of those will develop technological life.
Each of these steps that reduces the likelihood of technological life is called a "filter" in Fermi Paradox parlance. These vary from small filters to so-called "Great Filters". The idea of a Great Filter is almost no species gets beyond it. All the heavy elements we have access to might be a Great Filter.
As a reminder, anything heavier than helium is made in a star. Normal stars only make elements up to iron. It takes a supernovae or a neutron star merger to make elements heavier than this. So, for Earth to exist as is, there had to be a star relatively close to us that was the right size to basically go supernova. It had to be born, live and die before the Sun formed and that material had to be captured in our proto-planetary disk and ultimately become part of Earth.
We have thus far found absolutely zero evidence of these alien civilizations so the question is why? If we find an equivalent civilization to us on a really close neighbour then by Bayesian reasoning, it means it's significantly more likely that a Great Filter is still ahead of us.
Why does it seem like one of these stories pops up yet again every few years?
It might be because we keep discovering more exoplanets. So far we have confirmed 5830 of them ( https://exoplanetarchive.ipac.caltech.edu/ ).
Why is discovering another headline-worthy then?
For many reasons. 1 - it might be very unique itself 2 - it might be very close to us 3 - it might be orbiting a very interesting star, a star type we didn't expect to have that planet type or so many planets, or so close, or so far, etc 4 - the more exoplanets we discover the more we learn how star systems come to be. the more we know how rare ours is, how it might have formed, etc. It helps us answer age old questions.
"In the habitable zone".
I believe we have some of those, too, but very few. Another one is still a bit of a big deal.
> Unlike most planets in the Solar System, HD 20794 d’s orbit is not circular but elliptical
Kepler's First Law says otherwise.
It has an eccentricity of 0.40 (https://en.wikipedia.org/wiki/82_G._Eridani).
That's about twice as eccentric as Pluto/Mercury; Earth's is 0.016.
It's a reasonable layperson-friendly summary of the situation.
The orbits of planets in our solar system are quasi-circular, with only Mercury (e=0.20) and Mars (e=0.09) being more elliptical. Every other planetary orbit in our solar system has e<0.05, even 0.00x for Venus or Neptune.
They're not perfect circles but close enough for all practical purposes.
Meanwhile on Earth, UAP disclosure is kicking into full swing
How long until HN community picks up interest