Wednesday, December 1, 2010

ESO all steamed up about GJ 1214b

ESO today announced a stunning breakthrough in Spectrophotometery with a world first - analysis of the composition of a "super-Earth" exo-planet's atmosphere,...... and its steamy or hazy.

GJ 1214b is the first "super-Earth" to have its atmosphere analysed by astronomers and possibly water, in the form of steam, is the most likely explanation for what was found in the atmosphere.

In 2007 on Astronomy Cast, Dr Pamela Gay, talking about exo-planet research predicted "we will soon find our own little waterworld just waiting for a b-grade movie to be filmed on it." Well, waterworld it maybe, but this one has alot more steam than an Alfred Hitchcock shower!!!

On the 19th of November 2010 astrophysicists passed a major milestone with the discovery of the 500th exo-planet. An exo-planet is an extrasolar planet that orbits a star outside our own solar system. What are these planets, how do we find them, what are they made up of and how do we understand them?

A super-Earth is a rocky planet of 5-10 earth masses. These are of particular interest to astronomers as their likely orbits can fall in the potentially habitable zone around its parent star, where water could exist as a liquid.

Scientists use three primary methods to find planets around other stars, a radial velocity method, watching for micro-lensing events, and observing transits where the planet interrupts the line of sight causing its host star to dim.

GJ 1214b was discovered in 2009 on the HARPS instrument on ESO's 3.6m telescope in Chile. Initial suspicitions that GJ 1214b's density was too low to be composed only of solid material, therefore being a good candidate for an atmosphere, have now been confirmed by an international team of astronomers using the FORS instrument on the ESO's VLT (very large telescope).
Researchers Jacob Bean (Harvard Smithsonian Center for astrophysics), Eliza Miller-Ricci Kempton (Georg-August-Universitat, Germany) and Derek Homeier (University of California) have co-authored a paper to be published in tomorrow's edition of Nature explaining their detailed research.

"This is the first super-Earth to have its atmosphere analysed. We've reached a real milestone on the road to characterizing these worlds," said Bean.

The team were looking for one of three possible scenarios:
  • a small rocky planet shrouded in water/steam
  • an atmosphere of hydrogen obscured by dense high clouds and haze
  • a mini neptune like planet with a small rocky core and a rich hydrogen atmosphere
The observational method was highly complex and noted that there were no significant features in the specrum between 780 and 1000 nM ruling out the possibility of a rich hydrogen atmosphere.

Astronomer's use spectral analysis to determine the make up of an exo-planet's atmosphere. By monitoring the light of the parent star and looking for absorbtion lines at specific frequencies during the transit of an exo-planet, they compare the normal/reference light of the star for any differences and changes.

"Although we can't yet say exactly what that atmosphere is made of, its an exciting step forward to be able to narrow down the options for such a distant world to either steamy or hazy" said Jacob Bean. "Follow-up observations in longer wavelengths are required to determine which of these atmospheres exists on GJ 1214b".

Photo Credit ESO/L Carcada

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