Transiting extrasolar planetary candidates in the Galactic bulge

More than 200 extrasolar planets have been discovered around relatively nearby stars, primarily through the Doppler line shifts owing to reflex motions of their host stars, and more recently through transits of some planets across the faces of the host stars. The detection of planets with the shortest known periods, 1.2–2.5 days, has mainly resulted from transit surveys which have generally targeted stars more massive than 0.75 M ⊙ , where M ⊙ is the mass of the Sun. Here we report the results from a planetary transit search performed in a rich stellar field towards the Galactic bulge. We discovered 16 candidates with orbital periods between 0.4 and 4.2 days, five of which orbit stars of masses in the range 0.44–0.75 M ⊙ . In two cases, radial-velocity measurements support the planetary nature of the companions. Five candidates have orbital periods below 1.0 day, constituting a new class of ultra-short-period planets, which occur only around stars of less than 0.88 M ⊙ . This indicates that those orbiting very close to more-luminous stars might be evaporatively destroyed or that jovian planets around stars of lower mass might migrate to smaller radii. Planets in the limelight Most of the 200 or so extrasolar planets discovered to date were detected as 'wobbles' induced in their host stars by gravitational pull. But of late, transit surveys, based on detecting the dimming caused as a silhouetted planet passes repeatedly between us and the host star, have become increasingly successful at detecting new planets. A survey of 180,000 stars towards the Galactic bulge using the Hubble Space Telescope has uncovered another 16 candidate planets, with orbital periods of 0.4 to 4.2 days. Five of them, with orbital periods of less than a day, constitute a new class of 'ultra-short-period Jupiters'. They occur only around stars of less than 0.9 solar masses, suggesting that they never develop around higher-mass stars, or that they are destroyed if they do. A planetary transit search carried out in a rich stellar field towards the Galactic bulge discovered 16 candidates with orbital periods between 0.4 and 4.2 days, five of which orbit stars of masses with 0.44–0.75 times that of the Sun.