A Partly-cloudy Exoplanet

GPI images in the K1, K2, LP and MS bands, the emission of host star was blocked. The exoplanet 51 Eri b is indicated by an arrow.

Observing the first exoplanet discovered by the Gemini Planet Imager (GPI), 51 Eridani b, Abhijith Rajan (School of Earth and Space Exploration, Arizona State University) and his team used GPI spectroscopy and determined that the planet is redder than similar brown dwarfs seen elsewhere. "This might be due to presence of clouds, similar to young L-type planetary mass companions," said Rajan. "A possible reason for the presence of clouds, is that the planet is still in transitioning from a partially- to patchy-cloudy atmosphere, with lower mean surface temperatures."

The GPI observations, part of the Gemini Planet Imager Exoplanet Survey (GPIES), was combined with mid-infrared photometry at the W.M. Keck Observatory. These data allowed Rajan and his team to conclude that 51 Eri b appears to be one of the only directly imaged planet that is consistent with the cold-start scenario. The result is a low temperature and low luminosity planet.

Learn more about this result on the Gemini website.

The full results are accepted for publication in The Astronomical Journal. A preprint is available here.