Article Summary #7

The CoRoT-7 planetary system: two orbiting super-Earths

D. Queloz, F. Bouchy, C. Moutou , 2009, A&A, Volume 506, Number 1
http://www.aanda.org/index.php?option=article&access=doi&doi=10.1051/0004-6361/200913096

Due to the improvement of the searching methods of transient planets, many new exoplanets have been discovered lately and 50 out of hundreds transit their host stars. This type of observation (i.e. being able to observe a planet while it orbits a star) is very useful for detections because constraints can be put on the orbital inclination of the planet and the transit geometry can allow the calculation of the size and mass of the planet. This paper focuses on finding Earth-like planets orbiting the star named CoRoT-7.

The CoRoT Space Telescope is known for having been very useful due to its ability to identify numerous transient sources. The spectrograph on board of this telescope is called HARPS (High Accuracy Radial velocity Planet Searcher) and this is the instrument from which the authors of the paper received their data with which they conducted a radial velocity investigation and they also added ground based photometry data.

By looking at the radial velocity data, they observed a strong variability and a periodic signal which are caused by a transiting planet. Thus, they observed the planet CoRoT-7b, which before that was assumed to be a super-Earth (i.e. planet with similar chemical and atmospheric structure as the Earth, but with a higher mass) and they managed to calculate its mass with a certainty of 20%.

Along with the signal from CoRoT-7b, they noticed a second signal which they investigated in detail and found supporting evidence to attribute it to a second, coplanar Planet, CoRoT-7c. The most intriguing aspect of the results of the authors’ investigation was that both planets appear to be denser than Neptune, so they most probably have a solid/rocky structure like that of the Earth, which is a very important discovery in the search for Earth-like exoplanets.