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New Paper Explores The Prospects For Life Around M-Class Stars (arxiv.org)
Long-time Slashdot reader RockDoctor summarizes the significance of a new paper describing "The Habitability of Planets Orbiting M-Dwarf Stars":
Although Star Trek had a minor smattering of "M-class planets" -- a designation that tells one nothing of substance -- "M-class star" is a much more meaningful designation of color, with two size classes, the dwarfs and the red giants... an M-dwarf of 1/10 the mass of the Sun will burn for around 1000 times the time that the Sun does... Therefore, if humanity ever meets an alien species, the odds of them coming from an M-dwarf [system] are already high. If humanity ever meets an alien species that has been around a billion years longer than us and has technology we can't even dream of, then the odds of it coming from an M-dwarf are overwhelmingly high.
This new paper offers "a comprehensive picture of the current knowledge of M-dwarf planet occurrence and habitability," pointing out that most of these stars are apparently orbited by planets packed closely together, with "a paucity of Jupiter-mass planets and the presence of multiple rocky planets." And more importantly, roughly a third of those rocky planets are orbiting in a "habitable zone" -- far enough away from their stars to support liquid water.
This new paper offers "a comprehensive picture of the current knowledge of M-dwarf planet occurrence and habitability," pointing out that most of these stars are apparently orbited by planets packed closely together, with "a paucity of Jupiter-mass planets and the presence of multiple rocky planets." And more importantly, roughly a third of those rocky planets are orbiting in a "habitable zone" -- far enough away from their stars to support liquid water.
Although Star Trek had a minor smattering of "M-class planets" -- a designation that tells one nothing of substance
Then why did you bring it up?
And actually, in universe it tells you plenty. It tells you humans and most of the other bipedial humanoid life-forms which smatter the galaxy can survive on the surface and breathe the atmosphere. It also tells you it's likely to be littered with polystyrene rocks or to look a lot like parts of California.
systemd is Roko's Basilisk.
M-dwarves last for a trillion years while a sun-class star is good only for a few billions (ours is 4.5ba old and in a billion years Earth will be uninhabitable). Which matters exactly zilch when the whole Universe is only 13.8ba old, and you need a few star lifetime iterations to produce enough "metals" (for astronomers anything above hellium is a metal) for life to be viable.
There's indeed more dwarves than any other kind of stars, but then, their habitable zones are much smaller and they have other problems that are harmful to life in our sense, so they don't have any advantage. Wake me up in a trillion years or two, then life will be strongly biased to dwarf stars.
The creatures outside looked from Alt-Right to Antifa; but already it was impossible to say which was which.
Short version - some close-in planets will be tidally locked, but not necessarily all of them. And (as discussed), the fact that M-dwarfs covers more mass variation than the next three classes of stars combined (F-dwarfs, G-dwarfs like the Sun and K-dwarfs) so it would be safe to expect a considerable variation in the behaviour of planets around M-dwarfs.
Consider tidal locking in a system with an M-dwarf star, a "hot Jupiter" and our Planet of Interest (PoI). If in orbit around either the hot Jupiter or the star, the PoI might become locked. But with the three in relatively close interaction, the PoI could be disturbed between locking to one, or the other, or alternating, or spinning irregularly. Feel free to use a planet with an irregular - literally chaotic, even - rotation in an SF scenario of your choice.
Birds are not dinosaur descendants;birds are dinosaurs, for all useful meanings of "birds", "are" and "dinosaurs"
You're the idiot. M stands for Minshara, a Vulcan word.
Only the State obtains its revenue by coercion. - Murray Rothbard
This is probably true. But those stellar generations are not the generations of common stars (dwarf stars, up to, for example, the Sun's mass), but the lifetime of larger, faster evolving stars. You don't get metals further up the periodic table than carbon from a Sun-mass star. The lifetimes of such stars (say, more than 3 Sun masses ; I forget where the exact dividing line is for stars getting up to burning silicon to iron. It's somewhere near that mass.) is much shorter - more like a half billion years, The time for the ejecta from a supernova to become incorporated into the next generation of stars is more significant than the lifetime of the stars.
Interestingly, there is a fair correlation between the metallicity of a host star and it hosting a "super-Jupiter," but that correlation breaks down for smaller (Neptune-size and Earth-size) planets. While they still form around stars with a solar-similar metallicity on average, they're not more common around higher metallicity. That's odd. There's something going on there that works against the obvious expectation of how things go. I don't know about you, but I'd take that as a sign to pay more attention to observational data than theory.
The study was (as is normal) carried out with the assumption of the stability zone of liquid water as the criterion for "habitable zone". No other constraint. You might be interested in finding something that would find William Shatner attractive - even if only as food - but that's not the only thing "life" could plausibly mean. A prokaryote-grade of organism with a non-nucleic acid genetic system would be far more interesting than something that beat Shatner at chess with an RNA-world type genetic system.
Birds are not dinosaur descendants;birds are dinosaurs, for all useful meanings of "birds", "are" and "dinosaurs"
We could spend the next thousand years developing technology, populating the Solar System with our robots, then travel at 0.01c to the nearest 10 planetary systems, and still not have a species which is 1% older than today.
That's unobtanium-free physics, but I do gloss over the difficulty of crewing and running a generation ship for the thick end of a millennium. It might be easier to develop some form of suspended animation for wombs, and ship frozen embryos for robots to develop, once the robots have built a sufficient space industry at the destination.
I'm sure that I'm never going to see humanity's First Contact moment. If I wasn't dead when it happens, I'd be astonished if any human which even knew it's 21st century ancestors names were involved. (I don't know the names of any of my ancestors even 5 generations back, let alone 30 or so).
A species doesn't need to travel at a significant fraction of c in order to colonise the galaxy. Our society probably couldn't do it in any meaningful sense (are we the same society as a thousand years ago - do you speak Old English, or Norman Frankish?), and maybe our species would have speciated into multiple descendant species by the time they get into other spiral arms. But that isn't "never" - just a very long term plan.
Birds are not dinosaur descendants;birds are dinosaurs, for all useful meanings of "birds", "are" and "dinosaurs"