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flipmcf t1_itg15w7 wrote

This is something I haven’t seen make main stream space news often. The “Goldilocks Zone” is a real simplification for habitability.

From the stellar spectra I surveyed for Nstars back in 2000’s, a lot of these cooler stars showed emission spectra and the experienced astronomers were associating that data with flares. He called them “active chromospheres”.

And I expected these cooler, older stars to be more stable and well behaved than ours. Not true at all.

I still wonder if a Goldilocks planet around a M-dwarf with a healthy or very strong magnetic field could survive an active star like this.

I’m really hoping the abundant K and M-stars could prove to deliver some really long-lived habitable planets.

We get significant flares every 100-200 years? Right? And earth’s atmosphere has been around for at least a 500 Mya in one form or another. Maybe even 1Bya?

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Corkee t1_itgo9i0 wrote

One more point against habitable planets around M class stars is that they are likely tidally locked due to the close orbits around the star - even in the Goldilocks zone. Maybe the biggest M class star could have a non-tidally locked planet in its GZ, but that would have to be a young star I guess.

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ErrorlessQuaak t1_itgrhxe wrote

Planets orbiting m dwarfs are not necessarily tidally locked. Spin-orbit resonances likely play a big role in compact multi planet systems.

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OrokaSempai t1_itgqurh wrote

Pretty sure earth has had an atmosphere of one composition or another for like 4B years

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Strict-Currency2840 t1_ith7i3y wrote

I’m pretty sure the earth is like 4 billions years old so I don’t think that’s right

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OrokaSempai t1_ith8dks wrote

4.543B. 543M years is plenty for an atmosphere to form. Hell, oldest known evidence of life on Earth is 3.7B.

Anyways, here is a credible source

https://forces.si.edu/atmosphere/02_02_01.html#:~:text=(4.6%20billion%20years%20ago)&text=As%20Earth%20cooled%2C%20an%20atmosphere,from%20gases%20spewed%20from%20volcanoes

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flipmcf t1_itji6hh wrote

Thanks. My point is that our star is very well behaved and our magnetic field is quite reliable. Probably a combination of both.

I just googled and found that Venus has no magnetic field today. So I guess our star is pretty well behaved, and Venus has sone good gravity.

I’ve always thought that if the momentum / velocity of a gaseous molecule is greater than the escape velocity of the planet… bye bye gas! No H2 or He in earth’s atmosphere because at ‘earth temperature’ that gas just can’t remain captured by earth’s gravity.

But I don’t know if that’s an actual thing b/c I never researched it or did the math. It’s just a theory.

And slamming charged particles into a planet’s atmosphere at relativistic speeds is surely also a contributing factor to removing an atmosphere. - just to bring the conversation back on topic.

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Zprotu t1_itod3zu wrote

Question. We know the earth is 4.543B years old, but what exactly does this number mean? Technically, wouldn't the creation process of the earth have started right at the moment of the solar system's beginning? (i.e the exact second of the gravitational collapse of the giant interstellar molecular cloud, so 4.6B years ago, adding about 400M years to the age)

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OrokaSempai t1_itpn6iy wrote

At some point 2 grains of sand stuck together that would eventually become the earth, but is that actually the earth? Before the moon was formed in an impact with another proto-planet, it was not the same size or composition as today, so at that point it was also a proto planet. That impact was the final step to those proto planets becoming the Earth and Moon, so personally I would say the earth is 4.5B years old, the point it became its final mass. (Also, the cores of the 2 proto planets would have combined at that point giving the earth a large core and powerful magnetic field).

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Zprotu t1_itubxzx wrote

Well all that is definitely included in the creation process of the earth to what it is today. Its why I would consider the point in time when the 2 grains of sand got stuck together as the start of the earth. We are talking about the beginning of earth's creation process after all. And this process began exactly at the moment of the gravitational collapse of the interstellar molecular cloud, no? Wouldn't thinking that the earth is 4.6B years old be correct if you frame it like that?

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iqisoverrated t1_itkg7rb wrote

>This is something I haven’t seen make main stream space news often. The “Goldilocks Zone” is a real simplification for habitability.

It also completely ignores life that is not land based. Or different than humans.

I.e. the 'Goldilocks zone' theory is complete rubbish.

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