Editor's Summary
13 September 2007
Planets in the red
Most of the more than 200 known extrasolar planets orbit main sequence stars similar to our Sun. When the hydrogen in their cores runs out, they will become red giants that can easily reach and engulf inner planets. This will happen to the Sun in about five billion years. After that the fate of Earth is uncertain, but the discovery of a planet orbiting a post-red-giant phase star suggests that it may survive in some form. The planet is in orbit 1.7 astronomical units (AU) from V 391 Pegasi. The maximum radius of the red giant phase was about 0.7 AU, and the distance of the planet during main sequence phase 1 AU. This shows that planets with orbital distances of less than 2 AU (which by definition includes the Sun) can survive the red giant expansion.
News and Views: Extrasolar planets: The one that got away
Hanging around a star that has passed through its red-giant phase doesn't seem a likely place for a planet. But one planet apparently managed to avoid being engulfed by its bloated star — might others, too?
Jonathan Fortney
doi:10.1038/449147a
Letter: A giant planet orbiting the 'extreme horizontal branch' star V 391 Pegasi
R. Silvotti, S. Schuh, R. Janulis, J.-E. Solheim, S. Bernabei, R. Østensen, T. D. Oswalt, I. Bruni, R. Gualandi, A. Bonanno, G. Vauclair, M. Reed, C.-W. Chen, E. Leibowitz, M. Paparo, A. Baran, S. Charpinet, N. Dolez, S. Kawaler, D. Kurtz, P. Moskalik, R. Riddle & S. Zola
doi:10.1038/nature06143
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