The theorized evolution of the circumbinary planet PSR B1620-26 b. Credit: NASA.
Binary star systems can have planets ? although these are generally assumed to be circumbinary (where the orbit encircles both stars). As well as the fictional examples of Tatooine and Gallifrey, there are real examples of PSR B1620-26 b and HW Virginis b and c ? thought to be cool gas giants with several times the mass of Jupiter, orbiting several astronomical units out from their binary suns.
Planets in circumstellar orbits around a single star within a binary system are traditionally considered to be unlikely due to the mathematical implausibility of maintaining a stable orbit through the ?forbidden? zones ? which result from gravitational resonances generated by the motion of the binary stars. The orbital dynamics involved should either fling a planet out of the system or send it crashing to its doom into one or other of the stars. However, there may be a number of windows of opportunity available for ‘next generation’ planets to form at later stages in the evolving life of a binary system. (...)
Read the rest of Astronomy Without A Telescope – Forbidden Planets (523 words)
© Steve Nerlich for Universe Today, 2010. |
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Full story at http://www.universetoday.com/81631/astronomy-without-a-telescope-forbidden-planets/
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