Comments on: Gliese 581 c (confirmed!)

By: Hyperactive Hartley 2 has a split history | SpaceWeb

Hyperactive Hartley 2 has a split history | SpaceWeb — Wed, 12 Oct 2011 12:07:05 +0000

[...] planet was also detected by members of the systemic collaboration! See this post on oklo.org for more [...]

By: systemic - Just like in 1846

systemic - Just like in 1846 — Mon, 28 Apr 2008 03:47:55 +0000

[...] On the Systemic Backend, there are many candidate planets that have had their orbits characterized. As is usually the case with planet predictions, most of the candidates will wind up being spurious, but it’s definitely true that real planets orbiting real stars have been detected by the Backend user base. For example, Gliese 581 c was accurately characterized by the Systemic users several months before it’s announcement by the Swiss (see this post) and the same holds true for 55 Cancri f (see this post). [...]

By: systemic - “With all possible expedition”

systemic - “With all possible expedition” — Mon, 21 May 2007 02:14:06 +0000

[...] Unlike the case of Gl 581c, there’s no particularly compelling evidence for a second planet. In sifting through the various fits that have been submitted, one finds that a second planet with a mass similar to Uranus and a period of 53 days is probably the most likely candidate perturber, and using the console, I find an unpublishably high false-alarm probability of 49% for a planet “c” with these properties. (The discussion boards on the systemic backend indicate that the systemic users have also arrived at this conclusion.) [...]

By: Big News! An "Earth like" Exoplanet Is Out There. « DJ’ing, Music, Humour, Life

Sat, 28 Apr 2007 12:14:04 +0000

[...] “Systemic … characterizing extrasolar planetary systems.” (A good looking site). A thread on Bad Astronomy / Open Universe forum about this (linked through to a bigger thread). [...]

By: andy

andy — Fri, 27 Apr 2007 21:37:56 +0000

Extrasolar Planets Encyclopaedia now lists the planet having eccentricity 0.16 for planet c - what would that do in terms of pseudosynchronisation/capture into higher order spin states?

By: tribe.net: oklo.org

tribe.net: oklo.org — Fri, 27 Apr 2007 08:58:28 +0000

Re: New ‘super-Earth’ found in space…

Even if we don’t get a direct image for 5 to 10 years, things could get inter…

By: plagÃ¶Ã¶ri

plagÃ¶Ã¶ri — Fri, 27 Apr 2007 07:42:01 +0000

Hello all,

Thank you for all these interesting information and the simualation movie.

Obviously the mind has shifted slightly because the word “habitable” vanished from the title of the (original) document of April 4th: see here http://obswww.unige.ch/~udry/udry_preprint.pdf

By: systemic - Gl 581 — The Movie

systemic - Gl 581 — The Movie — Thu, 26 Apr 2007 22:19:26 +0000

[...] Habitable or not, Gl 581 c is pointing toward better worlds to come. As I remarked in the past two posts (1,2), we’re guessing that “c” formed beyond the snowline and migrated inward to its current position just outside the nebulous inner boundary of the habitable zone. [...]

By: Eric F Diaz

Eric F Diaz — Thu, 26 Apr 2007 21:28:04 +0000

Thank you, Darin. That was a very articulate and illuminating explanation of the question at hand regarding Gliese 581c. I look forward to seeing what Greg, Fortney and the others working on this question come up with in the future.

Eric

By: darin

darin — Thu, 26 Apr 2007 19:19:20 +0000

As you’ve all found, the habitable zone isn’t a terribly robust definition. The inconsistencies in temperature that you are getting are due to different albedos, i.e. how much of the incoming sunlight energy is absorbed. Andy’s formula above is the canonical way to calculate the effective temperature of a planet. Notice that albedo comes in as (1-A)^(1/4), so different albedos are important, but not overwhelmingly so. I think a more important difference, as mentioned above, is the greenhouse effect given that many of the most abundant molecules in the galaxy are greenhouse gases (water, CO2, CH4).

To answer plagoori’s question, you must remember that neither the mass nor the radius of this planet are acutally known. The mass is the “minimum mass” and, since radial velocity cannot determine the angle of the system, the mass could actually be much larger. I would be not surprised if it turned out that these planets are all Jupiter-size. The quoted radius of 1.5 Earth radii is the size that the planet would be if it were terrrestial, which is not known. We actually have no idea what the density of Gliese 581c is. This is why the transit technique is so useful… you determine the radius and you know the orientation of the system, so you also know the mass. These give you a density and then you can say that it is either a 5 Earth-mass puffball of Hydrogen or a 5 Earth-mass terrestrial planet likely to contain liquid water.

In any case, the planet should be synchronized or spin-locked to the star. If there is a substantial atmosphere, it is thought that heat redistribution would be pretty good and the dark-side of the planet relatively warm. Laughlin and Fortney are a few of the people working on this question with more detailed models, so pay attention to the site for more information.