Expert: Philip Stahl - 2/6/2011

Question
If Red Dwarfs lack Hydrogen, would their circumstellar cloud also have a reduced relative amount while searching Red Dwarf stars for water spectra signs and life, so would would not also a comet cloud around that system  leave an increased signature line at, say, H Alpha, c's, o's, AND N's on the red dwarf star's spectrum?

Answer
Hello,

It's hard to conceive that circumstellar clouds will be sustained around any red dwarf stars, far less any comet "clouds". Most of the former aggregate around more massive stars, and even the most massive red dwarfs simply don't qualify.

Because of the red dwarfs' small masses, any solar systems are bound to suffer a "compactiification" problem in that the planets are going to inevitably too close to the main star. (The same would hold for any cometary clouds).

Another aspect that hasn’t been mentioned too often is that the putative planet(s) more often than not appear to be tidally locked into its orbit with the red dwarf star, yielding conditions not conducive to either water or ice.  One of the system Gliese 581 planets, I believe 'd', indicates an orbital period of 37 days so that its year is about one tenth of a year on Earth. In addition, the tidal locking means one side of planet is always facing toward its Sun – the other side toward darkness.

No creature in its right mind would live directly in either of these extreme zones, since it would freeze in one and boil in the other. Thus, the only place to live would be exactly within a razor thin terminator zone straddling the extreme dark and light hemispheres. This zone would likely be about 100 miles wide at most, and so any intelligent life would have to confine their cities, civilization within this strip - no spreading out.

Further, some atmospheric modeling of this bifurcated world has yielded contradicting results. For example, under one numerical modeling all of the atmosphere freezes on the night side, which means it wouldn't be very much on the day side. However, the heavy gravity -much more than Earth- lends credence to the possibility that the atmosphere is fairly evenly distributed. Toss in a planetary greenhouse effect (which doesn't need humans to incept, btw - look at Venus) and there could even be equable warming which moderates the extremes somewhat.

My personal take is that I'd stick to stars (and their systems) higher in the spectral order (>F) to search for signs of water, or even primitive life, or cometary clouds.

(Note: you're not going to get any H-alpha lines- at least that you can actually discern- in a red dwarf's spectrum, since the hydrogen is constantly being consumed and fused to helium.)