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New planet discovered, "Gliese 581 c"

sundowning

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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?
 
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sundowning

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OP continued...

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/2007/04/25/earth-sized-planet-discovered-in-the-habitable-zone/
-http://www.eso.org/outreach/press-rel/pr-2007/pr-22-07.html
-http://www.scientificblogging.com/news/astronomers_find_first_habitable_earth_like_planet
-http://www.cbc.ca/news/background/space/space-water.html
-http://en.wikipedia.org/wiki/Gliese_581_c
 
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MacGuffin

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

I want little green men.
 

HilbertSpace

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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?
 

Siúil a Rúin

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

sundowning

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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

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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

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

HilbertSpace

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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.

Excellent - thank you.

I'm actually quite interested in exobiology, so yeah, this is a juicy tidbit.
 

Dark Razor

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Interesting, however, is it correct that the same side always faces the sun?
Wouldn't that mean that there are probably extreme storms on the planet?
There's also the possibility that two completely different types of evolution came about on the two sides of the planet, one based on chemical energy, like that of sea organisms in the lightless depths of the earth's oceans, and one based on energy gained from photons, like terestrial plants.
If the atmosphere is dense enough then there probably wont be such a high temperature difference between dark and bright side as the air mixes because of the temp gradient, but that would mean strong storms, possibly as permanent storm systems, like on Jupiter. I think it's questionable if terestrial life could develop under constant storms, sea life should not be affected by this though.
 

sundowning

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Interesting, however, is it correct that the same side always faces the sun?
Wouldn't that mean that there are probably extreme storms on the planet?
There's also the possibility that two completely different types of evolution came about on the two sides of the planet, one based on chemical energy, like that of sea organisms in the lightless depths of the earth's oceans, and one based on energy gained from photons, like terestrial plants.
If the atmosphere is dense enough then there probably wont be such a high temperature difference between dark and bright side as the air mixes because of the temp gradient, but that would mean strong storms, possibly as permanent storm systems, like on Jupiter. I think it's questionable if terestrial life could develop under constant storms, sea life should not be affected by this though.

One article briefly discussed this, supposing that the temperate regions would be near the edge of the lighted area (though not necessarily inferring the rest is inhabitable).

I mean, really - what do they know? That a planet exists, basically; it could feature a unique model of circulation, or it could be a planet with great extremes moderated only slightly by atmosphere.
 

darlets

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bleh, this can go here
"nternational astronomers say they have found the strongest evidence yet of the existence of the mysterious substance known as dark matter.

Scientists believe invisible dark matter accounts for 90 per cent of the universe's mass and holds together galaxy clusters.

Otherwise, galaxies would only have the gravity from their visible stars, which would not be enough to keep them from flying apart.

A NASA team using the Hubble Space Telescope has now detected what it describes as a ghostly ring of dark matter around a cluster of galaxies 5 billion light years away.

The massive ring measures 2.6 million light years across.

Although it cannot be seen, astronomer James Jee says scientists have mapped out the ring's shape using distortions it produces in light coming from distant objects behind it.

"This is the first time we have detected dark matter as having a unique structure that is different from the gas and galaxies in the cluster," he said.

"Although the invisible matter has been found before in other galaxy clusters, it has never been detected to be so largely separated from the hot gas and the galaxies that make up galaxy clusters.

"By seeing a dark matter structure that is not traced by galaxies and hot gas, we can study how it behaves differently from normal matter."

The US astronomers say they made the discovery accidentally while mapping the distribution of dark matter within the ZwC10024+1652 cluster in August 2006.

As they studied their data, the astronomers noticed a ripple in the dark matter, similar to ripples created when a stone is plopped into a pond.

Dr Jee says he was upset when he found the ring because he thought there was a flaw in the team's data reduction.

But he then found research published in 2002 suggesting the cluster under observation had collided with another cluster 1 to 2 billion years ago.

The collision occurred along Earth's line of sight and from this perspective, the dark-matter structure looks like a ring.

Dr Jee says the galaxy cluster collision "created a ripple of dark matter which left distinct footprints in the shapes of the background galaxies".

"It's like looking at the pebbles on the bottom of a pond with ripples on the surface," he said.

"The pebbles' shapes appear to change as the ripples pass over them.

"So, too, the background galaxies behind the ring show coherent changes in their shapes due to the presence of the dense ring." "
Astronomers discover 'dark matter ring'. 16/05/2007. ABC News Online
 

Geoff

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So if it is 20 light years away, we are seeing what it looked like in 1987, presumably.

Since then it could have been blown up by a Death Star. Just sayin', that's all.

-Geoff
 

wyrdsister

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So if it is 20 light years away, we are seeing what it looked like in 1987, presumably.

Since then it could have been blown up by a Death Star. Just sayin', that's all.

-Geoff


It's so weird that when you look up... you are looking at history.

Always amazes me.
 

MacGuffin

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So if it is 20 light years away, we are seeing what it looked like in 1987, presumably.

Since then it could have been blown up by a Death Star. Just sayin', that's all.

-Geoff

We were not in that sector.
 
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