Planet hunters double down with FOUR-STAR SYSTEM

Amateurs pluck nugget from Kepler data

By Richard Chirgwin, 15th October 2012

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A group of amateur astronomers trawling through the vast store of data captured by the Kepler spacecraft has helped turned up a gem: a planet orbiting a double star, with another two stars in a more distant orbit.

The discovery was made by Planethunters.org which, led by Yale University, lets “citizen scientists” (aren’t scientists citizens? - Reg) comb through the data. The new discovery has since been confirmed by the professionals.

The “circumbinary planet in a four-star system” has been designated PH1, and hailed for its “wow-factor” by NASA Kepler scientist Natalie Batalha at Ames Research Centre. She also lauded the “exemplary human cooperation – cooperation between scientists and citizens who give of themselves for the love of stars, knowledge, and exploration.”

So, what is PH1? – It’s probably a gas giant, at six times Earth’s radius it’s a little larger than Neptune, with a 137-day orbital period about the two stars at the centre of its system. The other binary pair is a long way out: around 1000 astronomical units – AUs – from the system’s centre.

The Planethunters say its mass is more difficult to pin down: “being in such a complicated system didn’t help”, but it’s no more than half the mass of Jupiter, making it certain that the object is a planet and not another star (since it wouldn’t have enough mass to ignite).

The Planethunters blog post identifies Kian Jek and Robert Gagliano as having made the initial discovery, with transits of the planet observed by Hans Martin Schwengeler, Dr Johann Sejpka and Arvin Joseﬀ Tan.

In this post, Jek and Gagliano outline the discovery process.

The discovery has been submitted to the Astrophysical Journal. ®

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