PDA

View Full Version : Red Dwarfs Have Teeny Tiny Habitable Zones



Fraser
2008-Jan-11, 06:40 PM
As space telescopes get larger and more sensitive, the search for Earth-sized worlds surrounding other stars is about to get rolling. But astronomers are going to need to know where to look. A team of researchers are working on a survey of nearby stars, calculating the habitable zones around them. When the search begins, astronomers [...]

More... (http://feeds.feedburner.com/~r/universetoday/pYdq/~3/215125059/)

Trakar
2008-Jan-11, 08:29 PM
As space telescopes get larger and more sensitive, the search for Earth-sized worlds surrounding other stars is about to get rolling. But astronomers are going to need to know where to look. A team of researchers are working on a survey of nearby stars, calculating the habitable zones around them. When the search begins, astronomers [...]

More... (http://feeds.feedburner.com/~r/universetoday/pYdq/~3/215125059/)

Perhaps not great candidates for forming Life as we know it, but they'd make good harbors for existent life. Those hab-zones may be tight, but they are incredibly stable and last for what something like 100Byears?

Noclevername
2008-Jan-11, 10:45 PM
Since the Habitable Zones are just estimates based on a single example, it's possible that the Red Dwarf zones are bigger or smaller than we think ("smaller" in this case would mean "practically nonexistent".) And there's always the old moon-of-a-warm-Brown-Dwarf-around-a-Red-Dwarf scenario.

Trakar
2008-Jan-12, 05:18 PM
Since the Habitable Zones are just estimates based on a single example, it's possible that the Red Dwarf zones are bigger or smaller than we think ("smaller" in this case would mean "practically nonexistent".) And there's always the old moon-of-a-warm-Brown-Dwarf-around-a-Red-Dwarf scenario.

Oh, we don't know what we don't know, but I've run some real simplistic calculations for the "habitable moon" senario, and its real tricky, especially if you are trying to use the Primary as a source of energy for surface life on the moon (at least light energy). Far enough away to keep from being continuously cooked/sterilized by radiation belts and yet close enough to get enough thermal/light energy. And as a moon, tidal-locking is always going to be a problem. I still haven't totally discarded the concept, but moon cradles are much more complicated than they look at first glance.

t@nn
2008-Jan-13, 02:15 AM
My heart sank when I read that article. After all the promising findings that a planet tidal locked around a red dwarf could have an atmosphere, now this. I wonder just how tiny their habitual zones are. I'm wondering how big the habitable zone would be for an M0 star, the biggest one. It would have to be bigger than the ones for smaller red dwarfs.

RUF
2008-Jan-13, 04:11 AM
"Habitable zones" can be increased if planets have massive greenhouse effects, or a shell of ice over an ocean. Also, life can exist at the bottom of oceans around vocanic vents.

This doesn' take into considereation the fact that water may not be needed for alien life. This insistance on liquid water for life is tiresome.

What about crystaline life-forms? Remember "alien" means "alien." We may not even recognize alien life when we see it.

What if life is found on Europa? It is not in Sol's "Habitable zone."

Noclevername
2008-Jan-13, 07:31 AM
This doesn' take into considereation the fact that water may not be needed for alien life. This insistance on liquid water for life is tiresome.

Not at all, it's practical, for two reasons;

1. We know by direct evidence that water-based life can exist, we don't know by direct (or indirect, for that matter) evidence that non-water-based life can exist.

2. For a number of physical and chemical reasons, liquid water is the solvent with the closest to ideal conditions for supporting the complex molecular interactions needed for life.


Now, it might be possible for life to exist without water. On the other hand, it might not. We just don't know. So we concentrate on the things we do know can support life.

neilzero
2008-Jan-13, 12:02 PM
Perhaps most important is: Not too violent corronal mass ejections as these can snuff out life for planets very close to a class M star. The planet not only needs to be about a million kilometers from the Class M star, but it needs one Earth mass or more and high average density, so it can retain a thick greenhouse atmosphere. Being tide locked to the star is a mixed blessing as it means the surface under the sun will likely be warm enough, but all the water may be trapped in a giant ice cap on the cold side of the planet. Likely we are better off with fast rotation, but both inner planets in our solar system rotate very slowly, so that is not encouraging.
Multi star systems such Centarii may occasionally partly melt the ice cap, except Centarii Proxima (class M) is presently too far from the class K and G stars to melt the ice cap, if Proxima has a tidelocked planet with a thick atmosphere. Is it likely Proxima will move closer to A and B in the next million years? Neil