Too Close for Comfort

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Science  15 Jan 2010:
Vol. 327, Issue 5963, pp. 251
DOI: 10.1126/science.327.5963.251-a

More than 400 planets have been detected orbiting stars other than the Sun, often with properties radically different from those of the planets in our solar system. Many, termed ‘hot Jupiters,’ have a mass similar to or exceeding that of Jupiter but orbit much closer to their host stars. Researchers believe that these planets could not have formed so close to the stars, and so must have formed at larger distances and then migrated to their present positions. Some are dangerously close to their host stars and may ultimately spiral into them. Such is the case with WASP-19b, the planet with the shortest period yet detected. Its period is only 0.79 days and its mass and radius are 1.15 and 1.31 those of Jupiter. The data collected by Hebb et al. using the WASP-South telescope suggest that WASP-19b has been spiraling into its host star throughout its lifetime and has spun up the star in the process. The processes that end the inward migration of planets are not well understood. WASP-19b may contribute to our understanding of the evolution of close-in planets and may provide information about the properties of its host star.

Astrophys. J. 708, 224 (2010).

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