Planet-Hunting, "Transit-Style"

Mercury Spring 2007 Table of Contents

Photo courtesy of G. White

by Bandu Jayawardene, Graeme White, David Blank, Alex Hons, Arie Verveer, and James Biggs

One of the most exciting astronomical activities of the last several years has been the search for transiting extrasolar planets—those orbiting stars other than our Sun. And of particular interest are those extrasolar planets, or ESPs, classified as "transiting."

When a transiting ESP's orbital motion carries it in front of its parent star, the planet blocks some of the star's light, and astronomers observe a diminution in the star’s brightness. How much the light decreases depends almost exactly on the ratio of the size of the planet to that of the star, and, as the spectral type of the star tells us its diameter, we can calculate the planet's diameter. In fact, this is the only way known at present for directly finding the diameters of ESPs and for indirectly inferring the ESPs' masses.

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