Could perpetual night support life?

[Johonebesus]

Last night I had a dream about a planet with no daylight. There was a gas giant instead of a moon, and the distant sun was just a very bright star. None-the-less the planet was relatively warm. There was a long, snowy winter, but the snow melted for a time in the summer, and there was plenty of plant and animal life and a modern civilization. I was given to understand that somehow the planet was bathed in lots of UV and infrared, so even though it was dark, there was plenty of radiation for photosynthesis and heat.

So, out of curiosity, is this scenario even remotely possible? Is there any way that a star or even a gas giant could generate enough radiation to keep a planet/large moon warm without generating much or any visible light? I'm guessing not, but I'm not quite 100% certain, so I thought I'd ask.



On a vaguely related note, I also dreamt that aliens brought in a giant sphere that completely encapsulated the Earth. With the Sun completely blocked out, how long would it take for the planet to get too cold to support life, days, weeks?

[Junghalli]

Technically I think it could happen if the local star emitted almost all its energy in spectra outside our visual range but it'd have to be a very weird type of star. Maybe you could say it's actually a giant alien artifact or something.

Also, you couldn't have photosynthesis on a planet like that, at least not as we know it. Would it be possible to have photosynthesis using something other than visual light?

[Balrog]

That's some pretty freaky dreams.

Anyways, it could be possible for life to exist, but I think it'd have to rely on the planet itself. Deep-sea life, at depths where sunlight can't reach them, are reliant on hydrothermal vents. Whether you could get something similar on dry land I don't know.

[TC Pilot]

I was given to understand that somehow the planet was bathed in lots of UV and infrared, so even though it was dark, there was plenty of radiation for photosynthesis and heat.

I'm pretty sure that would just kill everything.

[Junghalli]

I'm pretty sure that would just kill everything.

UV would, infrared (in sufficient quantities) could warm the planet while leaving it apparently dark. But it'd be a very unusual star that would emit that much infrared for that little visual light. Even a warm brown dwarf would still be luminous in the sky of a planet orbiting it.

[Jaepheth]

Could the gas giant be absorbing whatever frequencies the sun is emitting and re-emit them as infrared, while simultaneously shielding the planet from the deadly frequencies the star emits?

That'd mean the sun was not in direct line of sight of the planet for most of the year, followed by massive die offs when the star is visible with many of the local animals hibernating under ground during those times.

[Alyrium Denryle]

On a vaguely related note, I also dreamt that aliens brought in a giant sphere that completely encapsulated the Earth. With the Sun completely blocked out, how long would it take for the planet to get too cold to support life, days, weeks?

A long long time. Why? Hydrothermal vents.

[Shinova]

Discover has had tons of documentaries about buttloads of life that exist quite well in total darkness near the bottom of the ocean floor.

[Shinova]

Assuming of course that the lack of sunlight hasn't frozen the ocean completely solid.

[Feil]

You could easily have life in geothermically heated oceans under an ice shell.

You can't have high UV and high IR form the same source without high visible in between.

The following is marginally-informed guesswork and should be taken with a grain of salt.

Radiation-wise, there's no reason why you couldn't have a star that produced the bulk of its radiation in the IR range - all you need to do is bring its surface temperature down below around 3000K. There'd still be significant visible light, though, because even at the lowest temperatures needed to maintain fusion, there's visible light, and the colder the star gets, the closer a planet would need to be to get enough energy to support liquid water at the surface, since total energy drops off with temperature as well as having the wavelength of the radiation shifted to the right.

I googled around a little and found this pretty blackbody radiation graphic which might help.
http://hypertextbook.com/physics/modern ... n-law.html

For reference, our sun has a surface temperature around 6000K, and Proxima Centauri has a surface temperature around 3000K.

[Alyrium Denryle]

Assuming of course that the lack of sunlight hasn't frozen the ocean completely solid.

It almost cant... Not with the geologic activity that exists that deep, it will create a thermocline. Plus the high pressure would keep the water from freezing all the way

[SpacedTeddyBear]

So, out of curiosity, is this scenario even remotely possible? Is there any way that a star or even a gas giant could generate enough radiation to keep a planet/large moon warm without generating much or any visible light? I'm guessing not, but I'm not quite 100% certain, so I thought I'd ask.

Funny you should mention this, my astrophysics prof told us about a book he read as a child. He forgot most of the details, but he remembered that one of the worlds the main character visited had a star that put out its entire EM spectrum in the UV, thereby making it invisible. The reality is that while hotter stars' EM spectrum peak in the blue/uv range, they also emit light in the other visible parts of the spectrum as well.

[Feil]

Funny you should mention this, my astrophysics prof told us about a book he read as a child. He forgot most of the details, but he remembered that one of the worlds the main character visited had a star that put out its entire EM spectrum in the UV, thereby making it invisible. The reality is that while hotter stars' EM spectrum peak in the blue/uv range, they also emit light in the other visible parts of the spectrum as well.

I wonder - could get that effect (an invisible star that still heats) by gravitational lensing or refraction?

[Johonebesus]

On a vaguely related note, I also dreamt that aliens brought in a giant sphere that completely encapsulated the Earth. With the Sun completely blocked out, how long would it take for the planet to get too cold to support life, days, weeks?

A long long time. Why? Hydrothermal vents.

I was thinking more in terms of terrestrial life, like humans.

[wjs7744]

I was thinking more in terms of terrestrial life, like humans.

Well, for the earth to cool down significantly, your hypothetical sphere would have to absorb the heat radiated by the earth while simultaneously not radiating any down to it, and I'm not sure if this is even possible. The lack of light for photosynthesis would be much more dangerous, although I couldn't say how long it would be before we started to feel the effects of global oxygen deprivation.

[Sriad]

A moon orbiting quite close to a giant planet could well be warmed enough by tidal forces that life could exist.

There would be a shitload of tectonic activity though, IE Io.

[Darth Raptor]

I had a dream (nightmare, really) once about a planet where all the life was heterotrophic. Obviously, this is impossible, as it would violate thermodynamics. The salient point here is that any biosphere needs constant (or regular) energy input or it will die. The aforementioned volcanic world powered by tidal forces and/or internal nuclear decay could (theoretically) support a biosphere founded on chemotrophic producers, but suffice to say that world would look *nothing* like an Earth where it's always night somehow. If you really need that for a literary setting or whatever, you're better off using an artificial handwavium explanation.

[Akhlut]

Photosynthesis can operate with wavelenths other than visible light. Hell, there is fungus growing in Chernobyl that utilizes the radiation there for energy by using melanin to grow.