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Author Topic: Should the Goldilocks zone be refined?  (Read 1604 times)

Online chiralSPO

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Should the Goldilocks zone be refined?
« on: 25/02/2015 18:29:03 »
The sun ejects a substantial amount of protons and alpha particles, must of which we are protected from by the Earth's magnetic field. I would expect the sun to eject neutrons as well, from which our magnetic field would not protect us. Presumably, the distance from the sun (about 8 light minutes, or 150 million km) and the half-life of free neutrons (about ten minutes) is what prevents us from being bombarded with neutrons (the solar winds travel at about 400 km/s, so if neutrons were traveling at this speed, it would take approximately 6250 minutes, or 620 half-lives, to reach us, effectively shielding us completely)

Given that most of the stars in the observable universe are red dwarfs, which would have "Goldilocks zone" significantly closer to the star than ours is here, can we set a lower limit on the brightness of a star such that the distance at which one might find liquid water would also be more than some minimum distance from the star? (say 240000 km, or 10 half lives, assuming 400 km/s neutron speed--which might not be reasonable, how much slower might one expect the neutrons to go?) I guess Proxima centauri is estimated to have a habitable zone approximately 450000 km from the star (http://en.wikipedia.org/wiki/Habitability_of_red_dwarf_systems), which is likely on the dim end of the spectrum, and already considerably farther than my completely made-up 10 half life requirement...

Is this any farther away than this limit imposed by avoiding tidally locked planets?

I feel like having liquid water, but being constantly bombarded with neutrons (even if it's only a few neutrons per minute per square meter) would not qualify as a life-friendly environment.

Thoughts people?

[Mod edit- please phrase subjects as questions in line with AUP]
« Last Edit: 02/03/2015 16:58:16 by Georgia »


 

Offline evan_au

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Re: refinement of Goldilocks zone
« Reply #1 on: 26/02/2015 08:59:27 »
Quote
I would expect the sun to eject neutrons as well, from which our magnetic field would not protect us.

The reactions which produce energy in stars mostly produce protons, positrons, neutrinos and gamma rays. Apart from the ghostly neutrino, these all interact strongly with matter, and will not travel far from their site of production.

Solar fusion occurs in the Sun's core, which has immense pressures and temperatures (and the reactants are confined for a long time). These criteria do not occur to anywhere near the same extent elsewhere in the Sun.

The most common nucleus in the sun is a proton. Any free neutrons would combine with protons to form deuterium, preventing neutrons from escaping from the Sun.

Any neutrons striking the Earth's atmosphere would collide with the light nuclei in the atmosphere, slowing their speed, and forming isotopes of the atmospheric gases.

However, in practice most of the isotopes in the atmosphere are produced by cosmic rays from outside the stellar system - and the products of cosmic rays do reach the ground.

 

Offline alancalverd

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Re: refinement of Goldilocks zone
« Reply #2 on: 26/02/2015 20:06:28 »
The magnetic field certainly helps protect life on the surface of dry land, but that's a pretty unimportant and fragile part of the biosphere. The important stuff like primal evolution and recycling of dead matter all happens under the oceans and under ground, where extraterrestrial ionising radiation is unimportant.
 

Offline Ophiolite

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Re: refinement of Goldilocks zone
« Reply #3 on: 28/02/2015 06:58:25 »
Since serious consideration is being given to Europa, Enceladus and Titan as possible environments conducive to life, it seems we need to either abandon, or seriously adapt the concept of a Goldilocks zone. I certainly agree with evan and Alan that we need not be concerned with the potential problems caused by neutrons.
 

Online chiralSPO

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Re: Should the Goldilocks zone be refined?
« Reply #4 on: 06/03/2015 16:09:00 »
Thanks guys!
 

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Re: Should the Goldilocks zone be refined?
« Reply #4 on: 06/03/2015 16:09:00 »

 

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