Most Earth-like planet to date
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  regulus

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Celestial Watchman
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Posted: 2010-September-29 at 11:04pm | IP Logged Quote regulus

Another planet has been discovered around Gliese 581, this one is called Gliese 581 g (the 6th planet found in the system!!!) It's believed to have a mass around 3 or 4 times the size of the Earth, and it was discovered by the gravitational wobble method It orbits it's sun in 37 days and is tidally locked to the star. It is unofficially named "Zarmina"

http://arxiv.org/abs/1009.5733


http://www.nasa.gov/topics/universe/features/gliese_581_feat ure.html

http://news.sciencemag.org/sciencenow/2010/09/astronomers-fi nd-most-earth-like.html

http://www.telegraph.co.uk/science/space/8033124/Gliese-581g -the-most-Earth-like-planet-yet-discovered.html

http://www.space.com/scienceastronomy/gliese-581-star-system -tour-100929.html

So now everyone has a fascinating new destination for their art


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  JKelly

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Posted: 2010-September-30 at 12:27pm | IP Logged Quote JKelly

That's incredible!! It's so cool to think that we may have just found another planet full of people (or primordial ooze blobs)! I wish we had a way of getting there or at least getting some satellites in orbit so we could take a look and find out for sure.

Thanks for sharing Brian.



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  Fahad

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Posted: 2010-September-30 at 1:19pm | IP Logged Quote Fahad

I just read an article on UniverseToday titled "Could Chance for Life on Gliese 581g Actually Be 100%?". It appears the discoverer claimed that chances of life on this planet are a 100% because it is at the right distance from the star for water to be liquid, if there is any. His statement has gathered quite an opposition.

Nevertheless, the Gliese 581 system seems more interesting now, than ever!


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  EDG1

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Posted: 2010-September-30 at 1:45pm | IP Logged Quote EDG1

Yeah, I think claiming that there's a 100% chance of life is a bit much, but it's probably the most likely place that we've found for it so far. Hopefully this world will be targetted for more detail observation, and when the big planet-finding telescopes go up that can detect atmosphere composition we might know more about its suitability for life.


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  Fahad

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Posted: 2010-September-30 at 1:53pm | IP Logged Quote Fahad

Do you remember what atoms/molecules the astronomers will be looking for, when they search for life, apart from water? Carbon dioxide perhaps? 


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  JanL

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Posted: 2010-September-30 at 3:11pm | IP Logged Quote JanL

Well, the planet is three time the mass of the Earth,  just a little larger in diameter, and it is tidal locked with a red dwarf; all of which is very bad even though it is in the Goldie Lock zone.  Jan 
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  Augustus

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Posted: 2010-September-30 at 3:53pm | IP Logged Quote Augustus

Whether there's life or not, still incredibly awesome that
we've discovered it! Just think how many others there
might be out there... I wonder how tidal lock would
effect the development of life. Imagine if you lived on the
equator and the sun never, ever set. Very cool stuff
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  EDG1

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Posted: 2010-September-30 at 9:16pm | IP Logged Quote EDG1

JanL wrote:
Well, the planet is three time the mass of the Earth,  just a little larger in diameter, and it is tidal locked with a red dwarf; all of which is very bad even though it is in the Goldie Lock zone.  Jan 


I don't think it's bad at all. Higher mass isn't necessarily a problem - we don't know the density yet, which means it could be a big solid rocky planet like Earth or it could be a panthalassic planet covered by a very thick water layer. If it's the latter then the surface gravity would be around 1.17g and the radius would be about 10,300 km.

The tidelocking isn't necessarily an issue either. Yes, there'd be regions of permanent day and night, but the twilight band between could be pretty wide. If the planet has a solid surface and the orbit is a little eccentric then there could even be a day/night cycle in the twilight band as the sun bobs up and down above and below the horizon due to the orbital eccentricity.

None of this precludes a habitable environment. Of course, it doesn't necessarily mean that habitable environments are present either.


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  EDG1

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Posted: 2010-September-30 at 9:24pm | IP Logged Quote EDG1

Augustus wrote:
Imagine if you lived on the equator and the sun never, ever set. Very cool stuff


Tidelocked worlds don't really have an equator - they don't rotate relative to the star (their day length is equal to their orbital period), so it's not meaningful to say that they have an axial tilt either.

They have a sub-solar point (directly below the star, in permanent daylight) and an anti-solar point (on the diametrically opposite side of the planet, in permanent darkness). At the sub-solar point (SSP), the star is directly overhead, all the time. As you move away from the SSP the star will move closer to the horizon behind you.

At the boundary between day and night side, the star will be at (or just above/below) the horizon, and you'd have permanent dawn/dusk (hence this band around the terminator is called the "Twilight Band" or "Twilight Zone").

If you keep going toward the antisolar point (ASP), the dusk behind you disappears as the star goes further below the horizon, until you're in a region of permanent night.

Temperature distribution depends on the atmosphere. A modest atmosphere (thinner than Earth's) and a global ocean can distribute heat around the planet in such a way that water on the nightside might not freeze solid. If there's no atmosphere at all though then the dayside will be searingly hot and the darkside will be utterly frozen, its only heat being supplied by the planet's interior.


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  regulus

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Posted: 2010-October-01 at 1:04am | IP Logged Quote regulus

I agree, being tidally locked is not necessarily a bad thing, our Earth life cycle is built around day/night rhythms, but that doesn't mean life on a different planet has to be the same way. Also I've heard hypotheses where a tidally locked world would have winds that distribute heat toward the cold dark side (obviously never tested ) Also the Goldilocks zone isn't even that big of a deal IMO, life has an uncanny way of surprising us with the places it can survive (bottom of the ocean, buried frozen lakes in Antartica, miles up in the atmosphere)

I told Tom about this book a while ago, but if anyone is interested i would recommend the book "What Does a Martian Look Like?: The Science of Extraterrestrial Life" by Jack Cohen and Ian Stewart (also known as "Evolving the Alien: The Science of Extraterrestrial Life") Jack Cohen was the fellow who came up with the idea for the grendels in the book "Legacy of Heorot" and "Beowulf's Children" It's really an eye opener of a book, as it shows how little we really understand of how and where life evolves/forms in the universe

The thing that really wowed me was that it's only 20 light years away! It's essentially in our stellar backyard!


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