Dr. Joseph Harrington
UCF

University of Florida Astronomy Colloquium - Jan. 24th, 2007

The Pioneering Direct Measurements of Extrasolar Planets

Since the discovery of 51 Peg b in 1995, over 200 planets have joined the extrasolar menagerie. Most are vastly different from the planets in our solar system, with some sporting 2-day "years", others having highly elliptical orbits, and one smallish planet containing more heavy elements than does our entire solar system. Planets are exceedingly dim and close to their bright parent stars, so detection has so far been indirect, by measuring the effect of a planet on the light from its star. The many theories of extrasolar planets are thus vastly underconstrained. In early 2005, we used the Spitzer Space Telescope to achieve a first: direct detection of extrasolar planetary photons in the 24-micron passband as HD 209458b passed behind its parent star and reappeared. The number of such measurements now stands at five, of which three are from our group. In addition, indirect (transit) spectroscopy has provided meaningful upper limits and one detection. Together, these measurements usher in the age of extrasolar planetary science. Data in hand or soon to be acquired with Spitzer will give us the first orbital phase curves, seventeen new Spitzer photometric direct detections, and the first measurement of extrasolar planetary variability. Numerous additional studies are possible in Spitzer's remaining two years of life, with future space telescopes and dedicated missions, and even from the ground.