SSP seminar

Characterization of Super-Earth Exoplanets: Application to GJ1214b

Bjoern Benneke

Monday 22 October 2012, 12:00 pm
Pratt Conference Room, 60 Garden Street

One of the most profound questions about the newly discovered class of super-Earth exoplanets is whether these exoplanets are predominately mini-Neptunes with hydrogen gas envelopes or water-rich planets with thick water vapor envelopes. Published transit observations of the super-Earth GJ 1214b rule out the cloud-free hydrogen gas layer, but are currently not able to determine whether the lack of large spectral features is due to high-altitude clouds or the presence of a high mean molecular mass atmosphere.

In my seminar talk, I will describe a strategy to unambiguously distinguish between cloudy hydrogen-rich atmospheres and high mean molecular mass atmospheres, such as water-rich atmospheres, based on observations of the shapes of molecular absorption features in the near infrared. The described strategy forms the science case for an unprecedented 60-orbit Hubble Space Telescope program to observe 15 transits of GJ1214b.

I then present a reanalysis of the published transit observations of GJ1214b. I find that the published observational data suggest water vapor absorption in the atmosphere of GJ1214b at a confidence of 1.8-sigma. The possible presence of water vapor was revealed by combining observational evidence from different spectral data sets using a newly developed Bayesian atmospheric retrieval method. If water vapor is actually present, our new Hubble Space Telescope program will be able to confirm the presence of water vapor at high significance.


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