Jacob Bean, Kevin Stevenson, Jean-Michel Desert, and Marcel Bergmann
Ground-based Transit
Spectroscopy of an
Exoplanet Atmosphere
Using the Gemini Multi-Object Spectrograph, researchers help characterize the
atmosphere of exoplanet WASP-12b. The transit spectroscopy technique used —
until recently only attempted with space telescopes — opens the door for future
ground-based studies that will lead to a better understanding of exoplanet
systems, and even our own Solar System.
The Importance of Exoplanet Atmospheres
Recent telescopic surveys have revealed an amazing diversity of planets orbiting other stars.
This wide assortment of exoplanets offers both challenges and opportunities to astronomers
studying them. The challenge is to understand these objects from the perspective of a complete theory of planetary system origin and evolution, which is one of the main goals of modern astrophysics. In a broader context, the opportunity is a chance to study classes of objects
that may lead to a better understanding of how our own Solar System formed and evolved.
One key to understanding and exploiting the diversity of exoplanets is to study their atmospheres. Planetary atmospheres mediate the energy balance between incoming stellar
irradiation and outgoing self-luminosity and re-radiation. Therefore, a planet’s atmospheric
properties control its size and appearance.
A planet’s atmosphere also keeps a record of its origins and evolution. For example, the atmospheres of gas-giant planets make up a significant fraction of their total mass. Therefore,
they must be intrinsically linked to the planet-formation process. Lower-mass planets with
rocky, metallic, and/or icy compositions could also have primary atmospheres. These would
October2013
GeminiFocus
5