First potentially habitable planet found
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  megear1

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Cosmic Enigma
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Posted: 2007-April-24 at 9:06pm | IP Logged Quote megear1

Check it out:

http://apnews1.iwon.com//article/20070425/D8ON9PUO0.html

Yep, this link stopped working. AP feeds a bunch of different sources, so you've probably seen something already.

Mark



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  Hoevelkamp

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Posted: 2007-April-24 at 10:59pm | IP Logged Quote Hoevelkamp

Sorry Mark, the link is broken. But I read on a german site about that new found planet. It's in the "green" or habitable zone and it's supposed to have water. Temperatures between 0 and 40 Celsius and a year lasts only 13 days. It's mass is about 5 times earthmass and it's size about 1.5 times earthsize. It orbits the star Gliese 581 and is called "Gliese 581 c" (what a silly name for a planet is that?). Gliese 581 is 20 lightyears away. :(

Here's a link (unfortunately to a german site, but if you google for Gliese 581 you'll probably get what you want).

Spiegel Online

Ok, where can I book a flight?

Frieso

Edited by Craven


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  JanL

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Posted: 2007-April-25 at 10:06am | IP Logged Quote JanL

It's all over the NEWS networks too.  Since its so close, just wondering what type of life is present.  It appears that the temperature range is good.  However, if it is in tidal lock with the star, that's a minus and the gravity situation appears to be a problem too (for intelligent life).  Alabama cockroaches would probably thrive there (darn things can even fly--more or less).

By the way, the rendering of the planets and star:  The planets' crescents aren't correct--Jan

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  chaos

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Posted: 2007-April-25 at 11:05am | IP Logged Quote chaos

Admin's note: posts from similar thread moved here, to avoid thread abundancy.


Just announced, a planet of around 5 Earth masses around the red dwarf star Gliese 581, which may be in the habitable zone. Could be a giant ocean world but we don't have any idea of how much water the planet has got. It could well be a dry desolate rockball.

I'm somewhat sceptical about the habitability myself - I reckon it is warm enough to go runaway greenhouse, so unless it has a lot of water it will be a Venus-like planet rather than Earthlike, and even if it has enough water to be oceanic, the ocean may be near boiling point at its surface. If it has a sufficiently thin atmosphere to avoid runaway greenhouse it has probably all frozen out on the dark side (the planet is likely to be tidally-locked).

The Gliese 581 system is now known to have three planets, overview here.



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  nkalanaga

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Posted: 2007-April-26 at 1:57am | IP Logged Quote nkalanaga

That was also my take on it, and the authors of the paper agree.  The temperatures they quote are blackbody, not surface.  Earth's blackbody temp is about -20 C, and Venus' is about -40 C, due to its higher albedo.  So this world is already much warmer than either.  The authors gave -3 C if it s albedo is as high as Venus, which is still warmer than Earth, and +40 C for an Earth-like albedo.  It seems that the news folks got a little over-excited.  But the fact that we can find objects this small is itself progress.

They don't say much about the third world, d.  IF it has a thick atmosphere and plenty of water (not unlikely) it could have a surface warm enough for a global ocean.  The air pressure would probably be too high for us to breathe, though, and likely not breathable anyway.  But it could have some kind of life.  Several papers have mentioned the possibilty of such "water worlds", especially orbiting red dwarfs.  Essentially they form beyond the snow line, and are about half rock and half ice.  They then migrate inward in the same fashion as "hot Jupiters", but stop in or just beyond the habitable zone.  Visually they probably look like Venus, because the combination of thick air and high humidty should produce global clouds.

N Kalanaga

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  chaos

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Posted: 2007-April-26 at 5:21am | IP Logged Quote chaos

Actually, I reckon the third world is much more likely to be habitable. Depending on the actual luminosity of the star, the habitable zone may well extend out beyond 0.2 AU, which means that because of its elliptical orbit, the third planet might spend at least part of its orbit in the habitable zone. A thick, greenhouse gas rich atmosphere on the third planet would help things, rather than make the planet unpleasantly hot, and would also help stabilise temperatures throughout the year, making the effect of eccentric orbit less severe.

Finally, the elliptical orbit may mean the third planet is not tidally locked, but may be in a 3:2 spin state like Mercury. This would give the planet a day-night cycle lasting around 170 days for an orbital period of 80 days.
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  nkalanaga

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Posted: 2007-April-26 at 8:02pm | IP Logged Quote nkalanaga

The authors give the bolometric luminosity as 0.013 x Sol, and the idea of a 3:2 rotation sounds reasonable.  Even if it is tidally locked, a thick atmosphere and oceans, both likely, would spread the heat fairly evenly.  Photosynthesis wouldn't work on the dark side, but it seems somewhat impractical for what is probably a very cloudy planet, orbiting a dim star, anyway.  Chemosynthesis, as with our deep sea life, would work just fine, and there may be some photosynthesis in the brighter regions of the day side. 

Visual luminosity for Gl 581 is about 0.002 x Sol, so the light would look dim to us even in the habitable zone, as most of the output is infrared.

Once we get the technology, this would certainly be a good place to look for signs of life. 

N Kalanaga

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