New planet discovered, "Gliese 581 c"

[sundowning]

You may or may not have heard about this one. The news broke just recently, and it's getting a ton of buzz on the scientific side of the web. Reports of over 200, Jupiter-like (large, gaseous) exoplanets have been discovered in the past 10-or-so years, so what's the big deal deal with 581 c?

It's rocky.

It might have water.

It might be habitable.

With that in mind, it's not difficult to see why nerds, geeks, astronomers, astrobiologists, and whoever else might fit the bill are positively salivating.

A few stats on 581 c:

1) Located at an extremely close 20.5 light years away, it orbits the star Gliese 581 in the constellation of Libra. For context, the nearest star system to Earth is Alpha/Beta/Proxima Centauri at 4 light years away.

2) Gliese 581 is a red drawf star, relatively small with respect to our own Sun. Red dwarf stars are some of the most common in our neighbourhood; of the 100 closest stars to Earth, 80 are red dwarves. These stars have a life span of up to 100 times longer than our own Sun's estimated 10 billion years (5 of which have passed).

3) 581 c is estimated to be about one and a half times larger than Earth, with a mass of about 5 times greater. The density is reported at 8.1 g/cm^3 - Earth's is 5.5 (Mercury and Venus are 5.4 and 5.2 respectively. Mars is 3.9 g/cm^3). Those numbers may not mean much, but it suggests that 581 c follows the typical terrestrial model of a thin crust (< 2) and dense, diffrentiated core (10-12 g/cm^3) which is clearly much larger than the Earth's. Gravity is also stronger as a result of the increased mass, and 581 c probably has a stronger magnetic field (important for blocking star radiation).

(Of course, I'm thinking the flip-side of this coin is that if the core is so large, the mantle likely is too, and there's probably a lot of interior heat. If we look at the Moon, the patchy areas we can see with the naked eye and called 'Maria' (seas) are large basaltic lava flows that appear on the Earth-facing side as a result of the Earth's gravity. If we have a similar situation here with 581 c's synchronous orbit, it could mean the day side is (or at one time was) a volcanic mess like Venus.)

4) The planet is much closer to its star than is the Earth to the Sun, but as Gliese 581 is a red drawf, 581 c lies right in the habitable zone. It's in a synchronous orbit, meaning it rotates at the same rate it revolves, always presenting the same face to its star (much like the Moon always faces the Earth as a result of synchronous orbit). Its orbital period is 13 days.

5) Speculation about water is off the charts. As the surface temp should be within a 0-40C range, this certainly means that water could exist in liquid form. Some are even postulating 581 c contains vast oceans of water. I think they might be overly optimistic, but hey, it's possible, right?

[sundowning]

In a great interview here, a young astrobiologist explains a couple of methods they are developing which might one day be applied to planets like 581 c to detect things like a life-supporting atmosphere and if they have vegetation:

A small fraction of the light that reaches us from stars that have planets is transmitted or reflected from their atmospheres. By studying the spectrum of that light we can learn a great deal about them. What I do is build detailed models of planetary atmospheres, and use them to identify the signatures of life and how we can detect them.

Many of our ideas go back to the work of James Lovelock, who was really the first astrobiologist. He pointed out that if an atmosphere is completely in equilibrium, it’s likely that the planet does not harbour life. So aliens looking at the spectrum of Earth would notice the large quantities of oxygen and ozone there. Oxygen can be produced in the atmosphere of an abiotic planet, but not in the quantities that we see on Earth – and it’s very reactive, so you need a constant source to keep the level at 21%.

Oxygen is not the only biomarker. Another disequilibrium we are very interested in is called the red edge. A leaf is a complex structure of cells and empty spaces, in which sunlight is scattered back and forth. Photons that are good for photosynthesis are absorbed very efficiently, while the rest are scattered back as a waste product. This gives a very distinctive signature – a high reflectance in the far red of the optical spectrum.

So if you look at the spectrum of Earth from space you get this incredible increase of signal in the red part of the spectrum, which tells you that vegetation is there.

Cool, eh?

Sources and further reading:

-http://www.centauri-dreams.org/
-http://www.universetoday.com/2007/04...abitable-zone/
-http://www.eso.org/outreach/press-re.../pr-22-07.html
-http://www.scientificblogging.com/ne...th_like_planet
-http://www.cbc.ca/news/background/sp...ace-water.html
-http://en.wikipedia.org/wiki/Gliese_581_c

[wyrdsister]

Originally Posted by sundowning

With that in mind, it's not difficult to see why nerds, geeks, astronomers, astrobiologists, and whoever else might fit the bill are positively salivating.

*Salivates*

[MacGuffin]

Boring. Mars fits the same definitions of "inhabitable" used to classify 581 c.

I want little green men.

[HilbertSpace]

My understanding was that a star, prior to entering the red giant stage, would blow off an outer layer. If this is what happens, I think it would tend to radically alter the nearer planets (at the very least, blowing away the atmosphere and surface layers).

Am I misremembering my star lifecycles?

[HilbertSpace]

Originally Posted by MacGuffin

Boring. Mars fits the same definitions of "inhabitable" used to classify 581 c.

I want little green men.

I'd settle for little green bacteria.

[toonia]

Thanks for the interesting links, sundowning. I'll be back after reading them.

[sundowning]

Originally Posted by MacGuffin

Boring. Mars fits the same definitions of "inhabitable" used to classify 581 c.

I want little green men.

Except that from the first, Mars resides outside of the habitable zone in our solar system. Also, its noticably ellipitcal orbit makes it an unlikely target for anything we might be able to consider 'habitable', even with the unrealistic speculation for terraforming the planet.

581 c is the best candidate yet, and unlike Mars with 1/150th the atmosphere of Earth, has the potential to support a very decent one.

[sundowning]

Originally Posted by HilbertSpace

My understanding was that a star, prior to entering the red giant stage, would blow off an outer layer. If this is what happens, I think it would tend to radically alter the nearer planets (at the very least, blowing away the atmosphere and surface layers).

Am I misremembering my star lifecycles?

No, merely confusing the classification as I did last night on another board.

Whereas our Sun will enter the red giant stage and engulf the Earth at the end of its lifetime, red dwarves undergo no such process - they formed as is.

[nightning]

Hmmm interesting... perhaps we are getting one step closer towards finding intelligent neighbours. Thank you for sharing that.