Searching for Life in the Solar System ... And Beyond

A Research Discussion Meeting
London, UK - 31 October 1996


Keith Horne, University of St Andrews

Extra-solar planets can be discovered by gravitational lensing when a foreground star with a bound planet passes across the line of sight and amplifies the light of a background star. The highest density of suitable background stars is provided by the bulge stars that swarm around the center of our own galaxy. The detection probability scales as the square-root of the planet mass. For Jupiter-mass planets the detection probability is of order 10 per cent per stellar lensing event, and 50-100 such events can be monitored each year. Earth-mass planets can be detected by this method.

The St Andrews/SAAO Robotic Telescope Initiative aims to establish in South Africa a 1-metre Robotic Telescope equipped with a simultaneous optical/infrared camera to discover extra-solar planets by monitoring the gravitational lensing light curves. We expect to discover new planets around other stars at a rate of at least 5-10 per year, to build up a knowledge of the mass and orbit radius distributions of planets around different types of stars.