Apr 302012

Alien Life? Study Suggests Vast Number Of Planets Could Harbor It

Short form: recent studies indicate that the habitable zones around red dwarf stars could be wider than previously thought, with the possibility of perhaps tens of billions of planets in the galaxy where the surface temperature could support liquid water.

That’s the good news.

The more disappointing bit is that even a wider habitable zone around a red dwarf is still pretty close, meaning that the tidal forces on a planet that close in would be pretty severe. Thus if a planet has a spin rate so that it has a “day’ anything like 24 hours, the tides in any oceans could be monstrous. It is unlikely that a planet could hold onto any sort of moon for geological timespans given the orbital perturbations from that close star. Thus over a few billion years, perhaps just a few million, tidal drag would slow the rotation of a livable planet down so that it would be tidally locked with the star… one face perpetually lit by the star; one in perpetual darkness. Exactly how such a planet would be a really livable place is a bit of a stumper.

Still… on a *billion* such worlds, it’s a safe bet that life would arise many, many times, and at least some of the time, make a go of it.

 Posted by at 2:27 pm
  • Arlukiii

    A close orbit should be tidally locked. So no terrible tides, but a strong contrast between the permanent day and night sides. That may mean strong winds and storms. None of these things, including 100 meter tides, is a show stopper for life.

    • Anonymous

      > A close orbit should be tidally locked. So no terrible tides

      The terrible tides *result* in tidal locking. So until a planet locks itself to the star, the tides can be damned harsh. The only way to prevent tidal locking to the star would be to tidally lock with a moon. But that would probably be an unstable configuration that close to a red dwarf star, resulting in either the moon being torn away, allowing the planet to tidally lock to the star (after a rather horrific period where the planetary surface rebounds), or resulting in the moon crashing into the planet. Which is difficult to see as a good thing.

      > That may mean strong winds and storms.

      It may also mean the atmosphere freezing out on the dark side. Which would eventually lead to *all* of the air freezing solid. Which would be *bad.*

      As for 100 meter tides being a show stopper for life; current theory holds that basic life formed on Earth in tidal pools. This requires *some* tides, but not the kind of tides where the ground itself ripples and the oceans swamp miles inland.

  • Jordan

    Just given the sheer number of stars, having a billion or so star systems that harbor life is not improbable at all. I have a hunch that life may be more common out in the universe than we may have originally thought. There’s a good probability there is other life in this solar system or at least remenants of it.

  • My only interest in red dwarves is in putting Dyson Spheres around them, then living on the outside of the sphere. No tidal issues to worry about, and you can probably get enough stellar gravity to hold down a decent atmosphere. Not sure what the surface acceleration would be though. You’d probably have to genetically engineer yourself to avoid bone loss or suchlike.

    • Anonymous

      The outside of a Dyson sphere – the later sci-fi version with a solid shell, not the cloud of ecosystems Dyson actually envisioned – would seem a dismal place.

      As to surface gravity: take Proxima centauri as an example. According to wiki:
      Mass: 0.123 M☉= 2.46E29 kg = “M”
      Habitable zone ~0.023–0.054 AU. assume 0.03 AU = 4487936 km from surface
      Radius = 0.141 R☉= 98066 km

      So, radius from stellar center to surface of Dyson sphere = 98066+4487936 km = 4,586,002 km = 4,586,002,000 m = “r”

      Universal constant of gravitation = 6.673 x 10-11 m³/kg/s²

      Gravity acceleration at that mass & radius = > g = G* (M/r²) = 0.78 m/sec² (feel free to check the math). It’s not much, less than a tenth of a G, but it’s enough to give a good solid sense of “down.”

      The mass of the star would be more than adequate to hold onto an atmosphere. But the sheer mass of the atmosphere would be impressive (as would the shell). And I don;t know what would drive weather in the atmosphere… what would keep it from going stagnant? I can see up-and-down movement… the ground would be warm, and the sky cold; warm air from the ground would rise, radiate heat into space, cool off and sink. But whence come winds? Best I can come up with are “shades” orbiting within the shell; this would vary how warm the shell is from place to place.I guess that would drive winds.

      But it’d be dark. Bleah.

      • You’d need artificial lighting, granted. I’m thinking giant pillars with fiber-optic cores, ending in reflective lenses a few score miles up. The light would all be reflected downwards to the surface. Your sphere would look, on close examination, like a puffer-fish:-).

        I’ll take your numbers on the low gravity as correct. I expected a low surface gravity, so genetic engineering of the population would be necessary to avoid bone-density issues, and probably other problems related to low-g environments. But the amount of habitable area would make it worthwhile IMO.