| Radial velocity surveys of nearby, Sun-like stars have revealed a class of close-in, massive planets that orbit their stars with a separation of less than 0.1 A.U. I pursued two techniques that promise to reveal information about these objects that the Doppler measurements fundamentally cannot. First, close-in planets could produce a reflected light flux that is sufficiently large so as to permit it to be disentangled from the glare of the star. We placed the first significant upper limit on this effect for the extrasolar planet system tau Boo. Second, close-in planets will produce a measurable photometric dimming of the star if the planet transits the stellar disk. We made the first detection of such transits, for the extrasolar planet system HD 209458, proving that the star is orbited by a gas-giant planet. We pursued several follow-up measurements of this system. First, we observed the planetary transit simultaneously in several different colors, and used the color-dependence of the transit curve to break the degeneracy shared by the planetary and stellar radii, and orbital inclination. Second, we observed four transits of the planet with the STIS spectrograph onboard the Hubble Space Telescope. With the ultra-high precision afforded by these data, we refined greatly the estimates of the system parameters, and excluded the presence of opaque circumplanetary rings, and planetary satellites with radii significantly larger than that of the Earth. We outline a number of additional projects that are underway, including a search for absorption features of the planetary atmosphere, an attempt to measure the wavelength-dependent albedo of the planet, and an analysis of infrared observations of the secondary eclipse, with the goal of estimating the effective temperature of the planet. |
