Life in a brown dwarf "solar system"?

[Jak Nazryth]

I've been reading a lot about Brown Dwarfs lately. Unfortunately I cannot find an answer to my question, so I will just turn to a science fiction game (hello... Traveller) answer.

Everyone knows a Brown Dwarf doesn't give off as much heat or light as a real star. But does it give off just enough so that life might have a chance to evolve on one of it's "moons" / planets?

My science fiction answer is Of Course it can. It's science fiction.

But has anyone ran across any hard data that might indicate how much light is given off? I read an article of a BD about 50 times the mass of Jupiter who's upper atmosphere was estimated to be around 3k degrees fh, and the same article said (as with every other article I've found) that it doesn't glow as bright as a normal star.... so how bright is bright enough for photosynthesis etc... ?

Can life as we know it evolve around a brown dwarf?

 

[barnest2]

Brown dwarfs up to a gigayear old (a billion years) can have temperatures and luminosities similar to a main sequence star, so yes to begin with.
They will not settle into a set brightness like a normal main sequence star will though, so the system will slowly but surely get colder and colder.

 

[Rick]

Brown dwarfs up to a gigayear old (a billion years) can have temperatures and luminosities similar to a main sequence star, so yes to begin with.
They will not settle into a set brightness like a normal main sequence star will though, so the system will slowly but surely get colder and colder.

Yes - but the timespan involved in it cooling from a (barely) habitable level tp a completely uninhabitable level is still an extremely long time, long enough for some sort of life to evolve. Given that a planet would have to move in closer to the brown dwarf, be capable of some kind of atmospere and be in exactly the habitable zone during the timespan necessary to support life - the odds are extremely slim! :wink:

 

[Mithras]

bah photosynthesis...? Who needs that anymore for exotic alien life?
Thermal vents, caused by differential tidal effects, that's where life might be found ... why not around a brown dwarf?

 

[Reynard]

I checked Wikipedia concerning brown dwarf stars and planets have been detected:

The planetary-mass objects 2M1207b, GQ Lupi b and 2MASS J044144 that are orbiting brown-dwarfs, may have formed by cloud-collapse rather than accretion and so may be sub-brown dwarfs rather than planets.

Disks around brown-dwarfs have been found to have many of the same features as disks around stars, therefore it is expected that there will be accretion-formed planets around brown-dwarfs. Given the small mass of brown dwarf disks, most planets will be terrestrial planets rather than gas giants. If a giant-planet orbits a brown dwarf across our line-of-sight then since they have about the same diameter this would give a large signal for detection by transit. The accretion-zone for planets around a brown-dwarf is very close to the BD so tidal-effects would have a strong effect.

http://en.wikipedia.org/wiki/Brown_dwarf

Very interesting concept for a star system. "visible" light would be invisible to most known races as the star emits in the infra-wave. To humans the world is pitch black. Hey, what a story ide... oh.

A planet close enough would still be in the habitable zone and it would be still heated so liquid water would be possible. Essentially roll a world normally for atmosphere and water.

The chemical process to use infra-red light as energy for biological photosynthesis would be very different. As Mithras said there could be chemophagia. Mycological life could be the main land-based path. For ideas, see the japanese movie Matango (Attack of the Mushroom People).

 

[Jak Nazryth]

Big yes on thermal vents in deep oceans. But on the surface heat from volcanic springs etc.. would produce extra warm spots on the planets surface.
I am creating a world similar to the movie "Pitch Black" with creatures using many other kinds of senses rather than visible light. Granted, there still will be some light, but a bright day would be closer to dusk on earth. At least that's my best guess upon reading brown dwarfs and their output of visible light. A planet close enough to still get light, but far enough away not to be continually molded by gravity tidal forces similar to that on Io.

Also it is recently discovered site of yet another ancient experiment in human development. Humans were deposited on the planet as much as 100 k years ago as an evolutionary experiment.

I'm thinking of introducing a human sub-species based on 100 thousand years of evolution on a dark world. But just light enough to still have enough warmth etc... for a vibrant eco-system.

I'm not an astronomer, so any on the boards that might be able to figure out how long a "year" would be on a planet orbiting a brown dwarf?

Thanks

 

[BP]

Not an astronomer either!

But you might use http://www.calctool.org/CALC/phys/astronomy/planet_orbit

So distance (I use AUs - habital zone for BDs is small, near Roche limit - maybe 0.1 or less), mass of your BD (usually in Jupiter masses - but most are less than 0.07 depending on age, IIRC) and mass of planet are needed (this shouldn't really matter much for BDs, you can leave it at 1 earth).

 

[pasuuli]

For a good example of very-cold-low-light-helium-II-based sophonts, you need go no further than the Outsiders from Niven's Known Space.

 

[Mithras]

I'm thinking of introducing a human sub-species based on 100 thousand years of evolution on a dark world. But just light enough to still have enough warmth etc... for a vibrant eco-system.

While we're quoting movies.... How about The Descent, for a thumbnail sketch of humans living in a pitch-dark environment for millenia.

 

[PFVA63]

Hi,

For a long time I've had a thought of maybe trying to define vampires as an alien race stranded for eons on Earth. In general, having them be a species originally from a planet orbiting a brown dwarf might be suitable.

Being from a damp dark world might be a reasonable(?) way to explain their extreme sensitivity to the sunlight here. I also kind of thought that it might be possible to explain the need to sleep in a sealed coffin/sarcophagus lined with their "home soil" as relating to a need to "regenerate" in a sealed container laced with their home world's micro-organisms etc to repair the damages that our atmosphere and even night time lights may have on their bodies.

Anyway, just some thoughts.

Regards

Pat

 

[Prime_Evil]

For a good description of a civilisation inhabiting brown dwaf systems, read Permanence by Karl Schroeder - it's not his best novel, but it does contain some interesting ideas. The description of the planet Erythrion is very cool - easily the best thing in the novel.

 

[locarno24]

I'm thinking of introducing a human sub-species based on 100 thousand years of evolution on a dark world. But just light enough to still have enough warmth etc... for a vibrant eco-system.

Quick question - have the ancients just dropped them here, or have they done a bit of engineering first? Because 100,000 years isn't long for dramatic natural evolution.

I'm not an astronomer, so any on the boards that might be able to figure out how long a "year" would be on a planet orbiting a brown dwarf?

Depends entirely on how close you're orbiting...

One wiki (sorry) quote re planets: "The accretion zone for planets around a brown dwarf is very close to the brown dwarf itself, so tidal forces would have a strong effect"

On general principles, though, I'd say closer to the star - even accepting less light, cooler star equals a biosphere in a lower orbit.

 

[Rikki Tikki Traveller]

But, in this case, Tidal Forces are a good thing.

Tidal forces are what gives Europa a liquid ocean and (possibly/likely) life. No light from a star is needed, just heat and water (shaken, not stirred).

A world that would have a high enough surface temperature for life would be pretty rare, as mentioned above, the world would be almost at the Roche limit where tidal forces will tear it apart (see Saturn's rings). BUT, given the number of Brown Dwarfs estimated in the galaxy, there are bound to be a few that have a "habitable" planet (from a human perspective) around them.

Red Dwarfs would have similar effects as Brown Dwarfs, but are a bit brighter, so the habitable zone is bigger, making habitable planets a bit more likely (but still pretty rare).

 

[GypsyComet]

Local language might include references to "Warmrise" instead of "Sunrise". Of course, if there is significant water present, Warmrise will also be announced by huge waves.

Reading Robert Forward's Rocheworld books (also released as "Flight of the Dragonfly") might be of some inspiration here.