March 9, 2007
SPACE TELESCOPE SCIENCE INSTITUTE
"Worlds in Transit"
More than 200 extrasolar planets
discovered so far, all of them around
relatively nearby stars. The SWEEPS(Sagittarius Window Eclipsing
Planet Search) project used HST to monitor 180,000 stars in the
continuously for 7 days to look for transiting extrasolar planets. The
sample represents the farthest such sample, and includes stars down to
solar mass. We discovered 16 candidates with orbital periods between
4.2 days. In two cases, radial-velocity measurements support the
nature of the companions. Five candidates are ultra-short-period
(USPPs) with orbital periods below 1.0 day, something that had not been
before, and which occur only around stars of less than 0.88 solar mass.
indicates that those orbiting very close to more luminous stars might
evaporatively destroyed, or that jovian planets around lower-mass stars
migrate to smaller radii. The resulting frequency of planets in the
is similar to that in the solar neighborhood.