# US scientists find potentially habitable planet near Earth

post by Kevin · 2010-09-30T00:39:57.129Z · score: 1 (4 votes) · LW · GW · Legacy · 9 comments

http://news.ycombinator.com/item?id=1741330

comment by AlexMennen · 2010-09-30T01:26:33.335Z · score: 3 (3 votes) · LW(p) · GW(p)

The scientists determined that the planet, which they have called Gliese 581g, has a mass three to four times that of Earth and an orbital period of just under 37 days. ... If Gliese 581g has a rocky composition similar to Earth's, its diameter would be about 1.2 to 1.4 times that of the Earth, the researchers said. The surface gravity would be about the same or slightly higher than Earth's, so that a person could easily walk upright on the planet, Vogt said.

If it's mass is three times that of Earth and its diameter 1.4 times that of Earth, gravity would be 1.5 Earth gravities. A lighter mass would mean a smaller diameter, so a more realistic minimum would be 2 Earth gravities, which is what you get from assuming 3 times Earth mass and 1.2 Earth diameters. Thus, it seems a bit strange to say that the surface gravity could be about the same. True, a person could walk upright in that gravity, but it would not be comfortable.

comment by Kingreaper · 2010-10-23T11:44:23.085Z · score: 0 (0 votes) · LW(p) · GW(p)

"about the same" is a relative term.

If almost all bodies have gravities >10g, or <0.1g, then saying 2g is about the same as 1g is perfectly reasonable. Of course, by that standard all the inner planets in our solar system have about the same gravity.

comment by Will_Newsome · 2010-10-01T04:33:40.583Z · score: 2 (4 votes) · LW(p) · GW(p)

7 comments and no one's brought up the existential risks and anthropic (Great Filter) problems brought up by the fact there are potentially billions of Earth-like planets just within the Milky Way?!

comment by CannibalSmith · 2010-09-30T13:21:16.612Z · score: 2 (2 votes) · LW(p) · GW(p)

Now, all that's left to do is convince the world that nukes are not evil so we can build an Orion drive powered ship and colonize that planet.

comment by [deleted] · 2010-09-30T14:30:44.947Z · score: 1 (1 votes) · LW(p) · GW(p)

Sadly, 20 light years is not "near" enough to be useful in the near future.

comment by Jonathan_Graehl · 2010-09-30T20:59:14.312Z · score: 3 (3 votes) · LW(p) · GW(p)

Definitely not within the next 20 years :)

comment by nick012000 · 2010-09-30T04:02:15.191Z · score: 1 (1 votes) · LW(p) · GW(p)

The article says it's tidally locked, so it's probably not habitable. IIRC, it's entirely possible for enough of the atmosphere to freeze on the night side of a tidally locked planet to prevent Earth-like life from developing.

At best, though, it'd just be a thin equatorial strip between the day and night sides that would be habitable.

comment by AlexMennen · 2010-09-30T04:51:41.336Z · score: 0 (0 votes) · LW(p) · GW(p)

The article did mention that probably only the strip would be habitable. However, we even have examples of extreme-temperature microorganisms on Earth, so I don't think that we should rule out the possibility of life on the far or near sides. However, it is true that life is complex enough that the general probability of finding it on a given potentially habitable planet is almost certainly extremely low.

comment by nick012000 · 2010-09-30T04:58:19.416Z · score: 0 (0 votes) · LW(p) · GW(p)

If you want anything more complex than extremeophile bacteria, you'll need an atmosphere, and that's something you won't have if if all freezes on the "night pole".

Additionally, large bodies of liquid water would be scarce; if a lake extends onto the day side, it'll boil away until it doesn't. If it extends onto the night side, it'll be frozen, though I'm not entirely sure of what the fluid mechanics of the resulting situation would look like; you might get cycles of the ice building up and breaking off into the rest of the lake.