Mike Wall, Space.com (December 20, 2010)
"The alien planet Gliese 581g has been getting a lot of attention recently as a possibly habitable world, but a case is building for its next-door neighbor as a good candidate for extraterrestrial life, too.
"Gliese 581d, another planet discovered around the star Gliese 581, may well lie in the 'habitable zone' of the star - that just-right distance range that can allow liquid water to exist — new atmospheric-modeling research suggests. The finding follows closely on the heels of a similar study, published earlier this year, that reached the same provisional conclusion. [Tour of the planets around star Gliese 581.]
" 'The fact that two models find conditions for liquid water could exist, that strongly implies that it is possible,' said the new study's lead author, Philip von Paris of the Institute for Planetary Research at the German Aerospace Center in Berlin. 'It doesn't seem impossible to have life there.'
"The Gliese 581 system: Worlds of possibilities
"Gliese 581 is a red dwarf located 20 light-years from Earth, just a stone's throw in the cosmic scheme of things. Astronomers have detected six planets orbiting the star...."
Actually, the number of planets circling Gliese 581 is under debate. Some scientists who didn't discover Gliese 581g say it's not there: and they may be right. Or, not.
The Lemming thinks that, at this point, it's safest to say that there 'about a half-dozen' planets in the Gliese 581 system, and leave it at that.
Mr. Wall discusses what a "habitable zone" is, and how scientists crunched the numbers to determine what the odds are that water and a breathable-by-something atmosphere could exist on one or more of the planets around Gliese 581.
Star Trek's 'class M planets' notwithstanding, places that wouldn't look much like southern California could support life. Like central Minnesota, for example.
There's even a possibility that Earth is about as small as a planet can be, and still maintain a breathable atmosphere. ("Earth May Not Be a 'Class M' Planet" (December 5, 2009)) And that's (almost) another topic.
That year-old post isn't all that far afield, though: the Gliese 581 planets found (so far) are more massive than Earth. But not by much, in some cases.
As for some balmy tropic world inhabited by beautiful space princesses? That's another topic. ("Beautiful Space Princesses, Almost Certainly Not: Flying Whales, Maybe," Drifting at the Edge of Time and Space (December 8, 2009))
- "Gliese 581g: Then Again, Maybe So"
(October 14, 2010)
- "Gliese 581g? Maybe Not"
(October 13, 2010)
- "Gliese 581g, Space Aliens, and the Canals of Mars"
(October 12, 2010)
- "Gliese 581g, Alien Angst, and the Lemming"
(October 4, 2010)
- "Gliese 581g: Life? Maybe"
(October 2, 2010)