24 May 2001CfA Colloquium


Title: Transits by Extrasolar Planets: the Power of the Dark Side

Speaker: Timothy M. Brown

Abstract: Some of the planets of distant stars have orbits that are oriented so that, seen from Earth, the planet periodically transits the disk of its star. In this situation we have put a bright light behind the object we wish to study; with its help otherwise-impossible observations may be performed, and remarkably detailed inferences may be justified. I shall discuss three such applications of transit methods: (1) From the remote past (almost 2 years ago), the HST search led by Ron Gilliland for transiting planets in the globular cluster 47 Tuc. There turn out to be no such planets, or at least none detected. Why is that? (2) From the definite now, attempts to use spectroscopy to characterize the atmospheres of close-in extrasolar giant planets. By means of difficult (but feasible) observations, one has a chance to learn about clouds, temperature structure, composition, and even winds in the upper atmospheres of these planets. (3) From the far future (perhaps a decade hence) the use of transits to locate and even to study the atmospheric compositions of Earth-like planets of Sun-like stars.

Reference for students:

Lunch with the students will be on Friday, May 25th at 12:00 in A-101.