We're on our way already: Astroboffins find 5 potentially habitable Tatooine-like systems from Kepler 'scope Astronomers believe five binary-star systems identified by NASA’s now-defunct Kepler Space Telescope could have the right properties to support extraterrestrial life, according to new calculations. "Life is far most likely to evolve on planets located within their system's habitable zone, just like Earth,” said Nikolaos …
"Life is far most likely to evolve on planets located within their system's habitable zone, just like Earth,”
Life similair to that on Earth is likely to evolve on a place like Earth! Who'd have thunk it? In the meantime, we have to be a bit humble about what we actually know and especially what we don't about life.
For example one reasonable-seeming assumption is availability of liquid water as a medium bringing molecules together that can form organic compounds. Does this have to be water or could it be anything else? And are we assuming a liquid medium because that allows chemical reactions at the timescale on which life on Earth happens? Could a solid or semi-solid sludge hold life where the chemical reactions that make up life move so slowly that a simple 'creature' has a lifespan of millions of years with a 'metabolism' too slow for us to even detect? Or could a high-temperature plasma hold lifeforms that go through thousands of generations in a few instants?
Carbon is pretty weird and unique as an element and there are constraints on timing for complex chemical structures which mean you don't get them, even briefly, at very high temperatures.
But yes: we're looking for planets which might host the kind of life we know how to look for, because that is all we know how to look for. If we could work out other signatures for different sorts of life we'd likely be looking for those as well.
I have some sympathy with this. It would be disappointing if, a la Star Trek, everything in the universe worked like us. And I'm not sure we fully understand the extent of life on earth. (Remember those recent sponges on the bottom of the antarctic sheet?) But the laws of physics are the same for the everyone, water is a pretty special solvent, and the first thing life does is put up a fence and say "This is me. This is mine. I control here." (Cf the debate about whether viruses are alive.)
I wonder if both your life forms struggle with that latter problem. The mud monster is vulnerable to any physical process in its environment, especially when it exists on a geological timescale; it's not quite clear how it avoids having its delicate chemistry mixed up. The high frequency plasma flies seem even more implausible. Maybe you could get something like the gliders in the game of life in the great interstellar clouds. But anything close to a star will get washed way.
However, within our solar system, there is anticyclone that has maintained it's unique and disturbingly singular structure for centuries via no process that science has fathomed. It was recently postulated it was lysing. But it may be hunting a smaller but not dissimilar anticyclone and could renew itself by digesting this competitor. We don't have evidence it can reproduce but given it's longevity who knows. Anyway, what would it need for us to call it alive? If it had a mind, we definitely would - but I have no idea how to begin to communicate with it. At any rate, it could be life has been staring us in the face all along. Is it aware of us? Or at least, our affect on the earth? Perhaps a computation system, immeasurably different to ours, has been coveting the atmosphere of this small blue dot with envious photoreception. The good news - it can't invade; at least not until it has persuaded us to make certain environmental modifications. A trick, we would never fall for...
One of the most important reasons water (not just carbon) is the basis of life here is that it's amphoteric - it can act as either an acid or a base depending on the chemical environment it finds itself in, resulting (broadly speaking) in it being maximally useful in chemical reactions. It's an electrical dipole, resulting in hydrogen bonding that imparts lots of interesting properties to water, including cohesion and adhesion which contribute to both physical and chemical properties conducive to its support for life. Another important reason is that it's liquid at normal temperatures and pressures, which allows chemical activity at reasonable rates.
So although there may be other compounds or elements that could serve as a basis for life, nothing seems as suitable as water here.
I think the 'liquid at normal temperatures and pressures' thing is a slight miasma. Those temperatures and pressures are only 'normal' because they're the temperatures and pressures at which water is liquid. My friends who live on the surface of a neutron star think of those temperatures and pressures as grossly abnormal (but they are very, well, flat, and x-rays play an important role in their metabolism).
However the underlying point is obviously right: there are only so many elements, and we really know about all of the ones that are anything like stable (we think). We also know that at high enough temperatures that enough things are ionised there isn't time to build complicated structures (at this point I must not tell you that I am in fact a plasma-being and spend most of my time in the outer atmosphere of the Sun). And the properties of only some some small number of elements seem to be really suitable for building really complex sufficiently-stable molecules (and they fall apart at much lower temperatures than you need to ionise them, which reduces the temperature range further). So we could be wrong of course, but we're not being stupid.
It's not clear to me that life couldn't happen in solid water (ice in other words), with things gradually diffusing around. I suspect it probably could but the universe may not be old enough for it to have happened yet since the chemical processes would be so slow. My friends from Europa do rather laugh about this though: all that obsessing about a possible ocean under the surface is looking in the wrong place, of course: who would want to live in that messy liquid water, in the dark, anyway?
First of all, you assume the laws of physics are the same everywhere in the Universe which I sssume they might be not.
It's something like fingerprints in humans, we assume they are unique because nobody had the time and ressources to prove they are not.
It's not like fingerprints at all. We have never seen good evidence that the laws of physics vary over spacetime, and yes, we have gone looking for that because it would be interesting as fuck if they did (apart from anything else Nobel prizes, money and fame would pour onto anyone who showed this). So our working assumption is that it is extremely unlikely that they do. Which means, for instance, that chemistry works the same way throughout the observable universe, which tells us things about the possibilities of life which is built on chemistry. And, of course, for life which is nor built on chemistry: very many stars have plasma-beings living in their atmospheres, according to my plasma-being friends, anyway.
Our working assumption could be wrong, but we've never seen evidence that it is, and so when we go looking for things we try to make them make sense within the laws of physics we understand (when they're in a regime where those laws should apply).
Fingerprints are entirely different. If you assume fingerprints are just some random thing then you also know that they're not, in fact, unique: it's just rather unlikely that two individuals will have the same prints. You then just have to work out how unlikely. If they're not completely random then the probability of matches goes up (maybe related people have related fingerprints or something). So it's just a matter of time (perhaps a very long time) before we find pairs of matching fingerprints on different individuals: it's just the statistics we need to sort out.
Physical laws are just not like that, at all. When you go measuring the fine structure constant you're not looking at some statistical process where you expect, occasionally, it to be different ir something. (Note there is some evidence that it may vary over spacetime, but it's not very good evidence and the variation is very small if it's there.)
The formation of DNA and cell division I guess is the basic definition of "life as we know it". Does life need to meet our arbitrary qualification for it? Life takes another step in level when it becomes sentient, the threshold for this is somewhat fuzzy.
I'm open that the development of something other than organic cellular life forms could grow and that a sentient state could exist in some form other than an organic cellular platform.
From what I've been reading on the subject, water (the H2O kind) has a particular chemical property that makes it ideal for life. I don't remember if it's the fact that it can dissolve and mix stuff, or the fact that its abundance makes it a good target for researching planets with it, but water is just about as important as carbon.
There have been discussions about another element that could possibly combine some form of DNA, I think it was silica. Chemists and biologists are however not convinced that anything could actually evolve on that basis - if I'm not mistaken.
They haven't 'found 5 potentially habitable Tatooine-like planets': they've found that there are sets of orbits in these 5 binary systems where, perhaps, some number (which could be more than 5, or less (fewer?)) of potentially-habitable planets could live. There's no evidence at all that such planets do exist in these orbits, or that they don't. All they're really doing (which is very interesting) is showing that circumbinary orbits exist which might be in the habitable zone, which is not at all obvious since the annual variation in stellar flux would be pretty large. So that's really interesting given that most star systems are binaries, but it's not finding 5 potentially-habitable planets.
I realise the article text says this, but, really, misleading headline is misleading.
How can anyone in this world tell the size of Neptune ? Speaking for myself, I coldn't tell its size even if it would literally stand in front of me on my lawn. And now the same question if we move it a little bit further at about 3970 light years. Surely it's not 3975 or maybe 3865 ? I can't tell it from this distance.
I'm not joking, I would really appreciate if someone could point me to some common knowledge on this matter. How can we measure mass, distance, temperature etc. for things we can barely detect and are not in close proximity.
Well, first of all the things astronomers do to sort this sort of stuff out are really astonishing, and they do also depend on various assumptions, for instance that the laws of physics and various parameters to them don't change over distance. They might (it seems kind of unlikely) but then the entire 'observable universe' might be just painted on a giant projector screen somewhere: you have to start with some assumptions.
The following is also really oversimplified and misses out lots of cleverness. It is a good rule that, however clever you are, astronomers are cleverer than that (I am not an astronomer, but I know some).
Given that you can start by sorting out some relationships between the mass of a star, its colour (its surface temperature in other words) and its age based on models of how stars work. And in particular stars will spend a long time sitting on a place on what's called the 'main sequence', and during that time the relationship between their mass and their temperature is more-or-less constant. A star like the Sun will sit on its main-sequence for about 10 billion years (the Sun is ~ 1/2 way through).
So during that time if you can measure the colour of the star you know its mass. And you can test this for relatively nearby stars because you can get other measures of their distance, for instance by noticing how they seem to move in the sky as the Earth orbits the Sun, which lets you work out how far away they are using parallax. And that kind of thing confirms that this relationship between colour and mass works pretty well.
There's a complexity with measuring colour: stars have 'proper motions' meaning they're moving towards us or away from us which will shift their observed colour. And further away than that the expansion of the universe also shifts their colour, making them redder. Well, you can deal with this: you can look for absorption lines due to elements in the star's atmosphere, and you know where those should be, so by seeing where they are you can then shift the spectrum to the right place.
So now you can measure the colour of a star, and assuming its on its main sequence (and I think you can tell if it's left it) you therefore know its mass. And when I say that I mean you approximately know its mass and you have some idea how good that approximation is, of course: that goes for everything here!
And now you start doing really clever things. If you have a binary pair of stars then you can know the mass of each of them from their colours. And, either by directly observing them, or by looking at the shifts in their spectra over time, you can now work out things like the orbital period and orbital velocity of the two stars. And you can therefore solve the orbital mechanics of the system so you know things like their separation and so on.
But it turns out that you can do quite a lot of this for a binary system if you can only see one of the partners in it. If you're looking at some star and you can see it's wobbling towards us and away from us a bit you can deduce that there's another, dark partner object. If you're really lucky you might also see that dark partner pass in front of the star, which you can detect by noticing that the star gets a bit dimmer every once in a while.
And for some of these systems (not all) you can then solve this to get the distance and mass of the dark partner (pretty much the period of the wobble gives you the separation and how big the wobble is gives you the mass if you know the mass of the star, and if the dark partner is actually lined up right with respect to us).
And of course this 'dark partner' is a planet. And of course if you are very clever and measure lots of things about the wobble, then you can actually deduce that there must be several planets there, which sometimes you do.
And very occasionally (and completely astonishingly) you can actually directly see the things. here is an entry page for directly-imaged exoplanets, and it looks as if there are now hundreds of the things.
I think then that, if the planet does pass in front of the star you can use the timing of the light-curve as it does so to measure how big it is directly. If it doesn't I'm not sure what you do: perhaps people only know about the ones that do pass in front of their stars?
Like I said, this is a very sketchy answer: understanding what astronomers really do to work this all out is ... complicated.
I realised last night that there are really significant errors in this. In particular the bit starting 'And you can test this ...' is just confused: it's part of how you build a cosmological distance scale, not measure mass. And there may be other errors as well. I will leave it up as some of it may be useful, but read it with a cup of salt. Sorry!
"...at an average 1% of the speed of light, which we can't, it would take 400,000 years to get there..."
Even in the 24th century the Next Gen "Enterprise" could only muster about 4 LY per day....so, nigh on 4,000 LY would take around 1,000 days at Warp 9 - that's still about 3 years of travelling (including maybe some time to accelerate and decelerate at the start and end of the journey).
Of course if one went at Warp 9.5 or more then this would reduce the time...but given that "transwarp conduits" and "quantum slipstream drive systems" have yet to be invented, I doubt we should hold our breath waiting !
https://memory-alpha.fandom.com/wiki/Warp_factor#Star_Trek:_The_Next_Generation
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