SA Astronomers discover planets orbiting double star

Allen Versfeld's picture

Artist's impression of planets orbiting binary star UZ Fornax

Dr Stephen Potter and Dr Encarni Romero-Colmenero from the South African Astronomical Observatory (SAAO) have discovered evidence for an unusual extra-solar planetary system:  Two enormous planets distantly orbiting a tiny double star (UZ Fornax).  The binary pair in this instance are a white dwarf and a red dwarf, orbiting so closely to each other that they are able to rob material from each other's outer layers, causing periodic outbursts as the captured material gets thick enough to ignite.  The two stars are so close together that their entire orbit would fit within our own Sun, and takes just over 2 hours to complete.

They make up what is known as an eclipsing binary, where the plane of their orbit just happens to be perfectly aligned with us here on Earth.  From our point of view, they routinely eclipse each other and although their distance from us makes them look like a single star, we see the brightness dip periodically in a predictable and consistent manner.  Except that the SAAO team found that the timing of the eclipses isn't as precise as it should be, varying by as much as sixty seconds.  According to Dr Potter and his colleagues, the most likely explanation would be two planets, each many times larger than Jupiter, orbiting the pair of stars.  While the existence of these planets is not confirmed, their existence would explain the timing discrepancies.  You can read the paper announcing this discover here: http://arxiv.org/abs/1106.1404

 

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