Thursday, April 26, 2007

Exoplanet follow-up

Seems like I was just saying last week or so:
a group of scientists has published a paper arguing that M-class (Red) stars may be more hospitable to life than previously believed. There are a number of obstacles that life would overcome: M stars are dimmer, so the planet would need to be so close to the star...
Well, yesterday a group of scientists announced finding a possibly Earth-like planet orbiting a red dwarf star, Gliese 581.
The planet, Gliese 581c, circles the star every 13 days at a distance of about seven million miles. According to models of planet formation developed by Dr. Sasselov and his colleagues, such a planet should be about half again as large as the Earth and composed of rock and water, what the astronomers now call a “super Earth.”

The most exciting part of the find, Dr. Sasselov said, is that it “basically tells you these kinds of planets are very common.” Because they could stay geologically active for billions of years, he said he suspected that such planets could be even more congenial for life than Earth. Although the new planet is much closer to its star than Earth is to the Sun, the red dwarf Gliese 581 is only about a hundredth as luminous as the Sun. So seven million miles is a comfortable huddling distance.
What a strange world. Gliese 581c is probably tidally locked, meaning one side is constantly in daylight, and because it's so close, the local star would appear 20 times larger than our sun does in the sky, but the days would be dimmer and red.

As a side note, it's often said that the discovery of extraterrestrial life, more so intelligent life, would be a huge blow to the religions of the world. To which I say: please. These people don't believe in evolution, but we're going to convince them that we've found algae on Mars, or little green men orbiting a distant star?

3 comments:

Russell Borogove said...

the local star would appear 20 times larger than our sun

More like 6 times the size. Gliese 581 c orbits at ~0.07AU (14 times closer) but the star Gliese 581 is only about 0.4 times the size of Sol.

john said...

I was going off of this from the AP:

"But oh, the view. The planet is 14 times closer to the star it orbits. Udry figures the red dwarf star would hang in the sky at a size 20 times larger than our moon. And it's likely, but still not known, that the planet doesn't rotate, so one side would always be sunlit and the other dark."

Correct me if I'm wrong, but the moon and sun are equally large from the surface of the Earth, no? Hence, Earth's unique-looking eclipses? (A lunar eclipse on Mars is far less interesting, right?)

Cyrus said...

What a strange world. Gliese 581c is probably tidally locked, meaning one side is constantly in daylight, and because it's so close, the local star would appear 20 times larger than our sun does in the sky, but the days would be dimmer and red.

Call me stubborn, but I really insist that such planets should be called "Krypton-type planets," or Class K planets or something.

As a side note, it's often said that the discovery of extraterrestrial life, more so intelligent life, would be a huge blow to the religions of the world. To which I say: please. These people don't believe in evolution, but we're going to convince them that we've found algae on Mars, or little green men orbiting a distant star?

Algae on Mars would have no effect, you're right. If we found real, intelligent, extrasolar life capable of communicating with us, though, I think the effect on religions would be... not much greater than the effects on everything else, true, but still noticeable. A significant minority of religions, or of religious people, would treat it as a hoax, conspiracy, or the devil's work right up until they shook hands with an e.t., and probably after. However, I think it would push a lot of religious people either away from religion, or away from dogmatic, literalist versions of religion and towards the more deist, unitarian, impersonal versions. This is far from impossible; after all, it basically describes what happened with evolution in the first place. (If you'll forgive a bit of post hoc, ergo propter hoc. This is all saying "what if" anyway.)