Atmosphere of Exoplanets Sunday, Feb 25 2007
Astronomy and Astrophysics 7:00 am
From a NASA press release this week
NASA’s Spitzer Space Telescope has captured for the first time enough light from planets outside our solar system, known as exoplanets, to identify molecules in their atmospheres….
…
Spitzer, a space-based infrared telescope, obtained the detailed data, called spectra, for two different gas exoplanets. Called HD 209458b and HD 189733b, these so-called “hot Jupiters” are, like Jupiter, made of gas, but orbit much closer to their suns.The data indicate the two planets are drier and cloudier than predicted. Theorists thought hot Jupiters would have lots of water in their atmospheres, but surprisingly none was found around HD 209458b and HD 189733b. According to astronomers, the water might be present but buried under a thick blanket of high, waterless clouds.
Those clouds might be filled with dust. One of the planets, HD 209458b, showed hints of tiny sand grains, called silicates, in its atmosphere. This could mean the planet’s skies are filled with high, dusty clouds unlike anything seen around planets in our own solar system…
The ‘More Info’ page on the press release links to two papers “A Spectrum of an Extrasolar Planet”
by L. Jeremy Richardson et.al. and A Spitzer Spectrum of the Exoplanet HD 189733b by C. J. Grillmair et.al. apart from some podcasts.
And via BA Blog, we are reminded that “Twenty years ago, astronomers witnessed one of the brightest stellar explosions in more than 400 years. The titanic supernova, called SN 1987A, blazed with the power of 100 million suns for several months following its discovery on 23 Feb., 1987.” Of course, the article doesn’t quite spell it out that the neutrino detectors were telling us something interesting three hours before the explosion was seen ! (See this link too - via Backreaction blog .)

‘Rings’ left by the Supernova Explosion
May 30, 2007 at 12:03 pm
Yoy might find this preprint interesting
“The habitability of super-Earths in Gliese 581″
Abstract:
Aims: The planetary system around the M star Gliese 581 consists of a hot Neptune (Gl 581b) and two super-Earths (Gl 581c and Gl 581d). The habitability of this system with respect to the super-Earths is investigated following a concept that studies the long-term possibility of photosynthetic biomass production on a dynamically active planet. Methods: A thermal evolution model for a super-Earth is used to calculate the sources and sinks of atmospheric carbon dioxide. The habitable zone is determined by the limits of biological productivity on the planetary surface. Models with different ratios of land / ocean coverage are investigated. Results: The super-Earth Gl 581c is clearly outside the habitable zone, since it is too close to the star. In contrast, Gl 581d is a tidally locked habitable super-Earth near the outer edge of the habitable zone. Despite the adverse conditions on this planet, at least some primitive forms of life may be able to exist on its surface.
http://arxiv.org/abs/0705.3758v1
May 30, 2007 at 1:36 pm
Hi Parseval,
Thank you for that link. Indeed, I have not been able to follow up on the stream of exoplanet news that has been pouring out this month.
Some of them are very very interesting. For those who are interested, have a look at the “Systemic” blog which is dedicated to exoplanet news and another great blog titled “Centauri Dreams”.
You can see a discussion of the above paper at the post titled “Gliese 581: Right System, Wrong Planet?” at the “Centauri dreams” blog.
Exoplanet announcements are pouring in so fast lately that it has been near impossible to keep track !