NASA's Hubble Space Telescope and the W. M. Keck Observatory in Hawaii have made independent confirmations of an exoplanet orbiting far from its central star. The planet was discovered through a technique called gravitational microlensing.
Both of these techniques work best when the planets are either extremely massive or when they orbit very close to their parent stars. In these cases, astronomers can reliably determine their short orbital periods, ranging from hours to days to a couple years.
Donna Weaver / Ray Villard
Space Telescope Science Institute, Baltimore, Maryland
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University of Notre Dame, Notre Dame, Indiana
Institut d'Astrophysique de Paris, Paris, France