22 April 2010
22 April 2010
Speaker: Peter McCullough (STScI / Visiting Scientist at CfA)
Title:Discovery and Characterization of Transiting Extrasolar Planets
Abstract:In the past decade, one of the fastest growing fields of astronomy has been the
discovery and characterization of planets that pass in front of (or "transit") their host
stars. From telescopes in backyards to ones in space, observations of our "XO Project" and
many others around the globe are contributing to this burgeoning field of inquiry (e.g.
Garcia-Melendo and McCullough (2009) and others' discovery of the transit of the
HD 80606b). I will review highlights from some recent programs that I have had a role in,
using the HST, SST, and WIYN telescopes. In particular, time series photometry of high
precision with the Spitzer IRAC instrument have challenged the prevailing hypothesis for the
formation of hot stratospheres of such planets (XO-1b, XO-2b, and XO3-b; Machalek et al.
2008, 2009, 2010). Ground-based time-series photometry with a precision of 200 ppm per
minute, as demonstrated on XO-2 by Burke et al. with the WIYN 3.5-m, show promise for
discovering transits of super-Earths discovered by radial velocities. Time series of
spectrophotometry with Hubble's NICMOS instrument have provided initial glimpses to the
atomic and molecular content of transiting planets' atmospheres (HD 189733b, Swain et al.
2008; XO-1b, Tinetti et al. 2010). Prior to the May 2009 servicing mission of HST, we used
one of HST's fine guidance sensors, FGS-2r, as a photometer to observe the transiting planet
host star HD 17156 for ten straight days with a precision of 120 ppm per minute. We derived
the mean density of the star by two independent methods, the transit technique (Nutzman et al
2010) and asteroseismology (Gilliland et al. 2010), and find they agree, thereby validating
the two methods. I will also discuss some likely future developments enabled by precise
observations from space (Kepler, Hubble, Spitzer) and the ground.