Swallowing Planets

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Science  10 Oct 2003:
Vol. 302, Issue 5643, pp. 201
DOI: 10.1126/science.302.5643.201c

In January 2002, a star, V838 Monocerotis, suddenly brightened by about 6 magnitudes, followed by a slow decline. The star then repeated this outburst in February and again in March, leaving astronomers puzzled about what would cause such an unusual sequence of events. Retter and Marom suggest that V838 Mon swallowed three Jupiter-mass planets that were all orbiting within 0.5 astronomical units of the star; a very tight planetary system. V838 Mon probably started life as a main sequence star with a mass similar to that of the Sun, then the outer stellar shell started to expand as the star transitioned to a red giant. The expanding shell probably caught the closest orbiting planet in its grasp and pulled the planet into its interior. The gravitational energy generated by this planet-munching was used to throw off some ejecta, while the rapid release of a new source of hydrogen from the planet into the hydrogen-burning stellar shell produced the increase in luminosity. Once the process was started, the second and third planets were easy meals for the hungry star. — LR

Mon. Not. R. Astron Soc., in press, preprint astro-ph0309341.

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