Wednesday, January 13, 2010

Exoplanet's Spectrum Directly Measured



Astronomers have obtained the first direct spectrum – a “chemical fingerprint” – of a planet orbiting a distant, Sun-like star, providing direct data about the composition of the planet's atmosphere. An international team of researchers studied the planetary system around HR 8799 a bright, young star with 1.5 times the mass of our Sun, and focused on one of three planets orbiting the star. While the results were unusual and pose a challenge to current models of the exoplanet's atmosphere, the accomplishment represents a milestone in the search for life elsewhere in the Universe.

[...]

Bergfors added, “It took more than five hours of exposure time, but we were able to tease out the planet's spectrum from the host star's much brighter light.”

However, the spectra of the exoplanet's atmosphere shows a clear deviation between the observed spectral shape and what is predicted by the current standard models. “The features observed in the spectrum are not compatible with current theoretical models,” said MPIA's Wolfgang Brandner, a co-author of the study.

The models assume chemical equilibrium between the different chemical elements present in the atmosphere, and a continuous temperature profile (hotter layers below colder layers). At longer wavelengths (above 4 micrometres), the planet is significantly fainter than expected, which points to molecular absorption in its atmosphere. The simplest explanation is that the atmosphere contains less methane and more carbon monoxide than previously assumed.

“We need to take into account a more detailed description of the atmospheric dust clouds, or accept that the atmosphere has a different chemical composition than previously assumed,” Brandner said.


Science. It's soooo messy and unexpected. ;)

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