In the Spotlight: Small Planets Transiting Bright Stars
The number of known transiting planets has more than tripled in the years since Kepler was launched, mainly thanks to the abundant harvest delivered by the mission itself. Statistical analyses of these and the significantly more numerous Kepler planet candidates indicate that smaller planets are more common than large ones. Super-Earths (planets with radii between 1 and 4 R_Earth) are of particular interest because they constitute a class of objects which are not represented in our Solar System. Moreover, they can theoretically have a wide range of compositions which we are just beginning to explore observationally. While studies based on Kepler data have revolutionized many areas of exoplanet research, the relative faintness of most of the host stars in the Kepler field means that follow-up observations of these systems with other instruments is very difficult. Such observations include high-precision radial velocity measurements, interferometric measurements of the host star's radius and exoplanetary atmospheric studies, all of which contribute to the determination of the planets' properties. In order to better understand the nature of these widespread super-Earths, we therefore need to construct a sample of these objects that transit bright stars. At present, the most efficient way toward this goal is to photometrically monitor the predicted transit windows of known radial velocity planets with minimum masses in the super-Earth regime (< 10-15 M_Earth). The two such super-Earth transit detections so far, HD 97658b and 55 Cnc e, have already triggered numerous follow-up studies of these systems using both ground- and space-based instruments. I will discuss ongoing transit search programs with the MOST and Spitzer space telescopes - which are responsible for these detections - and summarize the current state of knowledge of these two systems.
Date: Jeudi, le 27 mars 2014 Heure: 11:30 Lieu: Université de Montréal Pavillon Roger-Gaudry, local D-460 Contact: René Doyon