"You take a million, billion tonnes of flaming inferno and turn it into 'twinkle, twinkle little star' ..."

Sat, 28 Apr 2007

Gliese 581 c : An Ocean Planet ?

Now that the weekend is here, I've been catching up on the news of this weeks big astronomy announcement: the discovery of a possible "Super-Earth" exo-planet, Gliese 581 c. This is the first exoplanet likely to be within the so-called "Habitable zone" around its star, where life as we know it could be possible. Unfortunately the Irish Times "World Apart" weekend supplement article has been quite disappointing.

Like Greg Laughlin at UCO Lick I get depressed when people give misleading information . It includes a very misleading "Artists impression" picture, simultaneously showing details we don't know and being incorrect about the few things we do know.

Its easy to get annoyed at the concentration of facts that are guesswork or probably wrong in this article. Gl 581c is not 5 Earth masses: thats its minimum mass: due to radial velocity measurements, we can only measure M sin(i), where i is the inclination, currently unknown. It could easily be far more, and hence all predictions of what the planet is like become moot.

Similarly, the radius is not necessarily 1.5 times Earths: thats a prediction, based on the mass, and current theories. Unfortunately, there is no mention that current theories of planetary size are coming under scrutiny as they fail to match other recent exoplanet discoveries. This makes other speculation about the planet such as the gravity on the surface quite misleading.

The BBC News summary is much better: it refers to the radius as "the radius should be", rather than "is". But it too includes the incorrect picture. While its article is couched in more conservative language, it doesn't explain what facts it quotes are speculation and why they may be wrong.

None of the media reports I have yet seen mention current missions, such as COROT, which is the most likely to find Earth-sized planets in the near future (launched late last year, it is due to finish its first observing run in April. Results awaited with anticipation). They also ignore Darwin and the The Terrestrial Planet Finder, the most likely missions to discover life on other planets, but currently sitting in funding limbo.

Concentration on purely the known facts would of course make the news reports short and boring. Instead they should emphasise more of the work of the scientists involved: we teach science as a set of cut-and-dried facts that often bore school students and drive them away.

Instead, when faced as the cutting edge of an important discovery like this, we could show how an amateur could be partially credited with getting this result; with the fact that, since the planet has a short "year" astronomers are already lining up to investigate transit measurements of it on May 7 and that with a magnitude of 10.6 (only 20 light years from Earth, after all) its within range of amateur astronomers to observe and determine its true size and details. How about getting people excited to get involved themselves?

The assumption that this planet matches the conditions for life is also premature in my opinion. Who said that all lifeforms need water and/or oxygen, in a temperature range from 0 to 40 degrees Celcius? We only know quite some about how it happened on Earth, but that doesn't mean the same conditions should apply elsewhere?
It doesn't make 581C more special than any other exoplanet in my opinion.
Indeed; current theories point to life evolving on Earth for the first
3 billion years without oxygen, and with temperatures well above
and below 0 - 40C : a hothouse earth, methane environment, with
episodes of 'snowball earth', where the temperature dropped well below
freezing, with life possibly only surviving in the Deep Ocean beneath
the ice. See "Rare Earth" by Peter Ward et al. for a good summary.

Hence my comment about "so-called habitable zones". Life on Earth
has existed, and continues to exist (2 -- 3 km under the surface,
in the deep ocean volcanic vents, etc.) in conditions replicated
all over the Solar system but well outside the established
"habitable zones".

What makes Gl 581c more interesting is :

* its small (possible) size. It makes Earth-like life more likely.
  * Another planet around a red-dwarf. 75% of the stars around our neck of the woods are red dwarfs, but current missions such as Darwin have red-dwarves listed as only 'secondary targets', with yellow stars such as our own being more favoured. This mission may change that.
  * Its star has a low 'metallicity' (ratio of heavier elements to  Hydrogen; see the discovery paper preprint for details. Until recently, it appeared that the
greater the metallicity of a star, the greater the chance of finding a planet. Now, as we discover smaller planets, they run counter to this trend. Perhaps a high metallicity is not required ? This has implications for how old stars with planets (and life) can be: older stars have lower metallicity. There is a greater chance of life being around for longer.  Interesting to see if this trend holds up.
Yes, I agree with you that most/all news reports on this wonderful, exciting discovery have been shockingly understated and disappointingly lacking in details. Most US news media almost totally ignored and hardly mentioned the discovery. DO YOU THINK THAT MAYBE THE REASON BEING THAT THE DISCOVERY WAS NOT MADE IN THE UNITED STATES, THUS BLARINGLY A FAILURE OF THE UNITED STATES TO REMAIN IN #1 LEADING POSITION????

As an artist (my website will soon be replaced by a new one - has none of my current works on it - which are far, far better than anything on there)) I am intrigued, and a little fearful of discovering intelligent life on another planet. However, I had always thought that I would be a very old woman when this discovery was made, so, I am DELIGHTED that all this is happening while I am not old yet.  I also feel that I have not yet painted my greatest art works, and so I am open to new input - VERY much so. (In the 1970's I painted a whole series of Mars Landscapes.) Anyhpw, yes, some new info should soon be available with the ALAN setup this summer. Thanks. - Brooke T.
I don't think that any lack of US coverage is due to a fall in pre-eminence of the US in this field: Astronomy like (most?) of the sciences is very international, and pays little attention to Nationality.  Even so, I that Geoff Marcys' group in UC Berkeley remains the Worlds most successful planet hunting group, so I don't think America could be said to be falling behind. (Though if any embarrassment in this area led to funding of NASA's Terrestrial Planet Finder, that would be good ...)

Instead, I think any lack of publicity in the U.S. is more due to fear of pushing Science in general, and this sort of astronomy in particular,  to avoid confrontation with creationists. This is due to a deliberate strategy of the religious right, the wedge strategy.  Discoveries such as this highlight that the debate is not between
Genesis and Darwin, but Religion and Science (or even Rational Thought) as a whole. Discovery of Earth-like planets undermines a biblical viewpoint of Earths special place; all astrophysics theories being based and dependent on billion-year timescales undermines a creationist viewpoint, showing the debate is not just about some nuances of "evolution" and "micro-evolution", but whether you believe an inconsistent book over the evidence in front of your eyes.

In terms of Artwork, I will try to post later some ideas of what exoplanets look like. Some good artists impressions would be really valuable: unfortunately with what media coverage there is, there is too much emphasis on pictures that have little or nothing to do with reality. See Systemic for some good models to draw inspiration from.
There has come winter :(
It became cold and cloudy!
Mood very bad :(
Depression Begins
Depression Depression Depression aaaaaaaa
HEEEEELP :( :( :(
I hate winter! I want summer!
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