8 ms·

Out of interest , although dimmer, are there any potential hazards simply due to the proximity of a dim star?

by ionwake 10y ago

rm_-rf_slash 10y ago
Actually they are fewer. A dim star has less high energy radiation and a lower probability of harmful solar flares.
- euyyn 10y ago
  But the danger of both of those things surely decreases with the square of the distance to the star?
- mkaziz 10y ago
  More radiation = more mutations = healthier/faster evolution!
  - jcoffland 10y ago
    Then the surface of stars ought to have more life than planets.
  - jonathansizz 10y ago
    That doesn't follow, at all. If we're talking about Earth-like life, then any such life would need protection from radiation to be able to live long enough to reproduce. If such protection wasn't provided by the planet's atmosphere, then life there wouldn't move out of the water. In any case, the mutation rate would need to be extremely low, as it is with Earth life.
  - Symmetry 10y ago
    Life is more than capable of evolving mechanisms to increase or decrease it's mutation rate. On Earth Eurkaryotic cells with large genomes have developed nuclei to reduce their mutation rate and bacteria are more of a mixed bag with some even deliberately uping their mutation rate above what would be cause by radiation, etc. So in the long run eukaryotic life would just have to waste more resources on mechanisms to resist the effects of the radiation.
- cgriswald 10y ago
  That's not quite true. These planets are very close to the star and can receive large doses of the little bit of harmful radiation that the star puts out. Additionally, these planets put out a lot of infrared, but not a lot of higher energy photons, and life-as-we-know-it needs those higher energy photons. That infrared is also absorbed by water in any atmospheres or oceans that are present, leaving even less for life. Finally, these types of stars tend to have rather variable output in their spectrums, which may make it difficult for life to adapt.
- antognini 10y ago
  That's backwards. Red dwarfs have extremely powerful flares relative to their luminosity. So much so that it's unlikely that life would survive on the surface of an orbiting planet. (Though life would probably survive underwater.) https://en.wikipedia.org/wiki/Habitability_of_red_dwarf_systems#Variability https://en.wikipedia.org/wiki/Habitability_of_red_dwarf_syst... https://en.wikipedia.org/wiki/Flare_star https://en.wikipedia.org/wiki/Flare_star
JumpCrisscross 10y ago
> are there...hazards simply due to the proximity of a dim star Tidal locking [1]. Similar to how our moon shines at us ass first all the time, the planets around TRAPIST-1 would be expected to have one face locked to their star. Instead of an equatorial belt bookended with loops of temperate zones, as we have on Earth, we should expect, climatically, an "equatorial" face and a "polar" face separated by a tropic-to-temperate transition area. [1] https://en.wikipedia.org/wiki/Tidal_locking https://en.wikipedia.org/wiki/Tidal_locking
- ionwake 10y ago
  Fascinating thank you
- noobermin 10y ago
  Of course, #askNasa didn't win me a question, but could any astrobiologists comment on this question: Tidal locking means the planets would always have a side facing the star, leading to very different thermodynamics in terms of climate and weather on the planet, not to mention radiation. Doesn't that very much hurt the chances for life on those planets?
  - Normal_gaussian 10y ago
    I would be very interested in seeing comparative weather simulations for a fictional tidal locked planet to Earth and the other Sol planets.
  - John23832 10y ago
    I'm not an astro-biologist, but I assume that it wouldn't be conducive to life as we know it, but that doesn't rule out all life.
  - SamBam 10y ago
    I don't see why. If anything, life might be even easier if you're constantly getting energy from above, rather than intermittently. In any case, "different climate and weather" doesn't seem to me to imply "hurt the chances for life." If they're in the habitable zone, then they're getting similar radiation as an organism at the far north latitudes of Earth are getting during the summer. I don't know if it makes that much difference to a short-lived bacteria whether it's full sunlight for several weeks at a time, vs full sunlight forever.
verandaguy 10y ago
Depending on the spectrum of the star, I would be concerned about non-visible radiation doses when in close proximity to the star. IANA astrophysicist, though. Actually, adding onto that, I'm wondering whether orbits this tight would result in a noticeable centripetal force -- that is, that you'd feel lighter on the night side of the planet than on the day side.
- mturmon 10y ago
  Good point, this is in TFA: "Although at least some fraction of each planet could harbor liquid water, it doesn't necessarily follow that they are habitable. TRAPPIST-1 emits about the same amount of X-ray and ultraviolet radiation as the Sun does, which could chew away at any protective atmospheres the planets might have." But it's complicated. For example, apparently the energetic radiation can help by stripping away the H/He atmosphere. For more, see: https://academic.oup.com/mnrasl/article-lookup/doi/10.1093/mnrasl/slw192 https://academic.oup.com/mnrasl/article-lookup/doi/10.1093/m...
fixermark 10y ago
Michael Okuda has raised the question on his Twitter feed of whether the planets would be close enough to the star that tidal force could be an issue---hard to say at this point (in the sense that they're not loose clouds of rocks, so tidal forces haven't sheared them apart, but I'd assume it's unclear whether they might have interesting geological activity, such as frequent earthquakes or unexpected extra heat due to internal friction).
semaphoreP 10y ago
Like others have pointed out, the combination of the planets being tidally locked so only one side gets sunlight and the strong X-ray radiation and flaring from the host star make it considerably un-Earth-like, and harder for life as we know it to develop.

Out of interest , although dimmer, are there any potential hazards simply due to the proximity of a dim star?

by ionwake 10y ago

Out of interest , although dimmer, are there any potential hazards simply due to the proximity of a dim star?

rm_-rf_slash 10y ago

Actually they are fewer. A dim star has less high energy radiation and a lower probability of harmful solar flares.

euyyn 10y ago
But the danger of both of those things surely decreases with the square of the distance to the star?
mkaziz 10y ago
More radiation = more mutations = healthier/faster evolution!
- jcoffland 10y ago
  Then the surface of stars ought to have more life than planets.
- jonathansizz 10y ago
  That doesn't follow, at all. If we're talking about Earth-like life, then any such life would need protection from radiation to be able to live long enough to reproduce. If such protection wasn't provided by the planet's atmosphere, then life there wouldn't move out of the water. In any case, the mutation rate would need to be extremely low, as it is with Earth life.
- Symmetry 10y ago
  Life is more than capable of evolving mechanisms to increase or decrease it's mutation rate. On Earth Eurkaryotic cells with large genomes have developed nuclei to reduce their mutation rate and bacteria are more of a mixed bag with some even deliberately uping their mutation rate above what would be cause by radiation, etc. So in the long run eukaryotic life would just have to waste more resources on mechanisms to resist the effects of the radiation.
cgriswald 10y ago
That's not quite true. These planets are very close to the star and can receive large doses of the little bit of harmful radiation that the star puts out. Additionally, these planets put out a lot of infrared, but not a lot of higher energy photons, and life-as-we-know-it needs those higher energy photons. That infrared is also absorbed by water in any atmospheres or oceans that are present, leaving even less for life. Finally, these types of stars tend to have rather variable output in their spectrums, which may make it difficult for life to adapt.
antognini 10y ago
That's backwards. Red dwarfs have extremely powerful flares relative to their luminosity. So much so that it's unlikely that life would survive on the surface of an orbiting planet. (Though life would probably survive underwater.) https://en.wikipedia.org/wiki/Habitability_of_red_dwarf_systems#Variability https://en.wikipedia.org/wiki/Habitability_of_red_dwarf_syst... https://en.wikipedia.org/wiki/Flare_star https://en.wikipedia.org/wiki/Flare_star

JumpCrisscross 10y ago

> are there...hazards simply due to the proximity of a dim star Tidal locking [1]. Similar to how our moon shines at us ass first all the time, the planets around TRAPIST-1 would be expected to have one face locked to their star. Instead of an equatorial belt bookended with loops of temperate zones, as we have on Earth, we should expect, climatically, an "equatorial" face and a "polar" face separated by a tropic-to-temperate transition area. [1] https://en.wikipedia.org/wiki/Tidal_locking https://en.wikipedia.org/wiki/Tidal_locking

ionwake 10y ago
Fascinating thank you
noobermin 10y ago
Of course, #askNasa didn't win me a question, but could any astrobiologists comment on this question: Tidal locking means the planets would always have a side facing the star, leading to very different thermodynamics in terms of climate and weather on the planet, not to mention radiation. Doesn't that very much hurt the chances for life on those planets?
- Normal_gaussian 10y ago
  I would be very interested in seeing comparative weather simulations for a fictional tidal locked planet to Earth and the other Sol planets.
- John23832 10y ago
  I'm not an astro-biologist, but I assume that it wouldn't be conducive to life as we know it, but that doesn't rule out all life.
- SamBam 10y ago
  I don't see why. If anything, life might be even easier if you're constantly getting energy from above, rather than intermittently. In any case, "different climate and weather" doesn't seem to me to imply "hurt the chances for life." If they're in the habitable zone, then they're getting similar radiation as an organism at the far north latitudes of Earth are getting during the summer. I don't know if it makes that much difference to a short-lived bacteria whether it's full sunlight for several weeks at a time, vs full sunlight forever.

verandaguy 10y ago

Depending on the spectrum of the star, I would be concerned about non-visible radiation doses when in close proximity to the star. IANA astrophysicist, though. Actually, adding onto that, I'm wondering whether orbits this tight would result in a noticeable centripetal force -- that is, that you'd feel lighter on the night side of the planet than on the day side.

mturmon 10y ago
Good point, this is in TFA: "Although at least some fraction of each planet could harbor liquid water, it doesn't necessarily follow that they are habitable. TRAPPIST-1 emits about the same amount of X-ray and ultraviolet radiation as the Sun does, which could chew away at any protective atmospheres the planets might have." But it's complicated. For example, apparently the energetic radiation can help by stripping away the H/He atmosphere. For more, see: https://academic.oup.com/mnrasl/article-lookup/doi/10.1093/mnrasl/slw192 https://academic.oup.com/mnrasl/article-lookup/doi/10.1093/m...

fixermark 10y ago

Michael Okuda has raised the question on his Twitter feed of whether the planets would be close enough to the star that tidal force could be an issue---hard to say at this point (in the sense that they're not loose clouds of rocks, so tidal forces haven't sheared them apart, but I'd assume it's unclear whether they might have interesting geological activity, such as frequent earthquakes or unexpected extra heat due to internal friction).

semaphoreP 10y ago

Like others have pointed out, the combination of the planets being tidally locked so only one side gets sunlight and the strong X-ray radiation and flaring from the host star make it considerably un-Earth-like, and harder for life as we know it to develop.