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Wolf 1069B: Earth-mass planet in the habitable zone of a nearby, low-mass star

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Re: Wolf 1069B: Earth-mass planet in the habitable zone of a nearby, low-mass star

#51

Post by moloch-hai »

nakedrobot2 wrote: post #45
moloch-hai wrote: post #40

None of these "habitable" planets is really plausibly habitable. In particular, orbiting so close, they are all tidally locked 1:1 to their star, presenting always the same face. If they have any water, it is frozen on the dark side. But they might have no water anyway because they (might!) have no magnetic field to fend off the solar wind that would take away all their hydrogen, as happened to Venus. Earth has its b…

If they're one in a billion, there are still billions of them.

But only a few thousand in our immediate galaxy.

Re: Wolf 1069B: Earth-mass planet in the habitable zone of a nearby, low-mass star

#52

Post by defrost »

moloch-hai wrote: post #40

None of these "habitable" planets is really plausibly habitable. In particular, orbiting so close, they are all tidally locked 1:1 to their star, presenting always the same face. If they have any water, it is frozen on the dark side. But they might have no water anyway because they (might!) have no magnetic field to fend off the solar wind that would take away all their hydrogen, as happened to Venus. Earth has its b…

Tidal locking doesn't equate to "always presenting the same face".

For example,

> Mercury .. is tidally locked with the Sun in a 3:2 spin–orbit resonance, meaning that relative to the fixed stars, it rotates on its axis exactly three times for every two revolutions it makes around the Sun.

> As seen from the Sun, in a frame of reference that rotates with the orbital motion, it appears to rotate only once every two Mercurian years.

> An observer on Mercury would therefore see only one day every two Mercurian years.

https://en.wikipedia.org/wiki/Mercury_(planet)

Re: Wolf 1069B: Earth-mass planet in the habitable zone of a nearby, low-mass star

#53

Post by moloch-hai »

bagels wrote: post #49
moloch-hai wrote: post #40

None of these "habitable" planets is really plausibly habitable. In particular, orbiting so close, they are all tidally locked 1:1 to their star, presenting always the same face. If they have any water, it is frozen on the dark side. But they might have no water anyway because they (might!) have no magnetic field to fend off the solar wind that would take away all their hydrogen, as happened to Venus. Earth has its b…

Mars and Venus are not tidally locked. Earth, Jupiter and Ganymede have magnetic fields, and Mars used to. Do we know that these exosolar planets don't have moons, don't have magnetic fields, and are tidally locked?

Mercury and Venus are very near to being tidally locked, despite being thousands of times farther from the sun than the planet cited is from its star. Mars is a good distance off.

Earth got its moon via a nearly, but not quite, fatal collision. Probably most other planets did not.

Ganymede's magnetic field is news to me. I don't think we know exactly what gives a body a magnetic field, or how it is maintained, but rotation seems to be important. Ganymede's is much, much weaker than ours, and some suggest it is a remnant frozen into rock.

Re: Wolf 1069B: Earth-mass planet in the habitable zone of a nearby, low-mass star

#54

Post by moloch-hai »

defrost wrote: post #52
moloch-hai wrote: post #40

None of these "habitable" planets is really plausibly habitable. In particular, orbiting so close, they are all tidally locked 1:1 to their star, presenting always the same face. If they have any water, it is frozen on the dark side. But they might have no water anyway because they (might!) have no magnetic field to fend off the solar wind that would take away all their hydrogen, as happened to Venus. Earth has its b…

Tidal locking doesn't equate to "always presenting the same face". For example, > Mercury .. is tidally locked with the Sun in a 3:2 spin–orbit resonance , meaning that relative to the fixed stars, it rotates on its axis exactly three times for every two revolutions it makes around the Sun. > As seen from the Sun, in a frame of reference that rotates with the orbital motion, it appears to rotate only once every two M…

Mercury is a very interesting case.

But it is much farther from the sun than announced planets are from theirs.

Re: Wolf 1069B: Earth-mass planet in the habitable zone of a nearby, low-mass star

#55

Post by vkou »

danw1979 wrote: post #47
nakedrobot2 wrote: post #45

Earlier quoted context omitted.

If they're one in a billion, there are still billions of them.

… but so far apart we’ll likely never meet or even hear from them ?

We're likely never to meet or hear from them even if they were a mere 5 light-years.

It's easier for Michael Jordan to jump to the Moon, than for man to travel to the nearest star.

Re: Wolf 1069B: Earth-mass planet in the habitable zone of a nearby, low-mass star

#56

Post by vkou »

danw1979 wrote: post #48
BeefWellington wrote: post #32

Earlier quoted context omitted.

Kepler-452b has 2X Earth gravity. Eternal leg day. But seriously, these are all too far away for us to reach in any of our lifetimes, barring some insane discovery that breaks all the rules as we know them.

Fusion propulsion, clever shielding and general relativity gets you anywhere in the galaxy in your lifetime, or so I thought …

You 'only' need to maintain a steady 1g acceleration for years, rather than seconds.

(What's a mere six orders of magnitude when it comes to physical engineering, anyways? Just spin up a few more jobs on the borg clusters, and if that doesn't work, Moore's law will rescue you in a decade or two...)

Re: Wolf 1069B: Earth-mass planet in the habitable zone of a nearby, low-mass star

#57

Post by defrost »

moloch-hai wrote: post #54
defrost wrote: post #52

Earlier quoted context omitted.

Tidal locking doesn't equate to "always presenting the same face". For example, > Mercury .. is tidally locked with the Sun in a 3:2 spin–orbit resonance , meaning that relative to the fixed stars, it rotates on its axis exactly three times for every two revolutions it makes around the Sun. > As seen from the Sun, in a frame of reference that rotates with the orbital motion, it appears to rotate only once every two M…

Mercury is a very interesting case. But it is much farther from the sun than announced planets are from theirs.

(again) Spin–orbit resonance means that "Tidally-locked" doesn't equate to "always presents the same face.

which leads to:

> But it is much farther from the sun than announced planets are from theirs.

a) So?

b) Is it really? I mean sure, in an absolute sense - but what about in an appropriately scaled sense, allowing for the 1/sixth decreased sun mass and the inverse square force relationships, etc.

c) Even so, see a) - How does this alter the fact that tifally locked doesn't equate to "always presents the same face".

To be clear, I'm just highlighting the fragile and dubious nature of your earlier assertion about tidal locking.

Re: Wolf 1069B: Earth-mass planet in the habitable zone of a nearby, low-mass star

#58

Post by loxias »

adastra22 wrote: post #44
loxias wrote: post #41

Earlier quoted context omitted.

I am not a biologist. I could be entirely wrong in which case please educate me. :) My understanding was that life would be "detected" by finding chemical signatures in the atmosphere which could not exist at a "steady state" without biological creatures there doing things. Is this what you mean by telltale signatures? (A++ username)

Yes, astrobiologists distinguish between direct detection of life and biosignatures. The latter are things for which we don’t have non-biological explanations at this time, but which we don’t consider adequate evidence by themselves for life. FWIW we’ve already detected bio signatures for life in the atmosphere of Mars (seasonal methane emissions). And maybe Venus, though that is less clear. (Thanks!)

Thanks for this, your phrasing makes the concept more clear.

Can you give a (fictitious as necessary) example of what would constitute "direct detection of life", from an astrobiological perspective? Given our window to the universe is through telescopes I'm having difficulty imagining/distinguishing how to draw the line between "observed data for which we don't have any non-biological explanation" and something even stronger.

Like, does "direct detection of life" only include "we sent something there and found life"?

> we’ve already detected bio signatures for life in the atmosphere of Mars (seasonal methane emissions).

And ~Europa~ Enceladus too, right? ~ISTR seeing some paper about plumes of water vapor, as well as chemistry for which we don't have any non-biological explanation.~ I found it -- I was thinking of in 2017 when H2, CO2 and CH4 were detected at a ratio in thermodynamic disequilibrium .

Edit: I'm guessing "direct detection" in an astrobiological context would be something that builds on "direct detection" in an exoplanet context, a concept I already understand a bit -- friend of mine wrote her thesis on direct detection and imaging of exoplanets 15 years ago. :)

Re: Wolf 1069B: Earth-mass planet in the habitable zone of a nearby, low-mass star

#59

Post by sph »

vkou wrote: post #55
danw1979 wrote: post #47

Earlier quoted context omitted.

… but so far apart we’ll likely never meet or even hear from them ?

We're likely never to meet or hear from them even if they were a mere 5 light-years. It's easier for Michael Jordan to jump to the Moon, than for man to travel to the nearest star.

Weird popsci analogy.

Travel to the nearest star takes a very long time. Michael Jordan can train for thousands of years and will never leave atmosphere with his jump.

Re: Wolf 1069B: Earth-mass planet in the habitable zone of a nearby, low-mass star

#60

Post by moloch-hai »

defrost wrote: post #57
moloch-hai wrote: post #54

Earlier quoted context omitted.

Mercury is a very interesting case. But it is much farther from the sun than announced planets are from theirs.

(again) Spin–orbit resonance means that "Tidally-locked" doesn't equate to "always presents the same face. which leads to: > But it is much farther from the sun than announced planets are from theirs. a) So? b) Is it really? I mean sure, in an absolute sense - but what about in an appropriately scaled sense, allowing for the 1/sixth decreased sun mass and the inverse square force relationships, etc. c) Even so, see a…

Literally all moons in the solar system are tidally locked, 1:1, to their parent body. That is the norm for tidal locking.

Mercury, lacking ocean or even atmosphere, and mostly frozen solid, is accorded leeway a putatively-habitable planet does not get.

Word games are tiresome. Mercury's 2:3 spin-orbit resonant "lock" is interesting but off topic.

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