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Several planets in our solar system have multiple moons. But in other planetary systems the orbital dance can get far more compelling. Astronomers are finding that some faraway worlds orbit multiple suns.
Lots of stars are bound up in binaries, where two stars orbit each other. And astronomers using NASA's planet-finding Kepler spacecraft recently found two different binary star systems that each host a planet.
The idea of such circumbinary planets has been a popular one in science fiction. Just think of Tatooine, the desert world from Star Wars, with its two suns hanging low on the horizon.
The newfound planets Kepler 34 b and 35 b are gas giants about three quarters the diameter of Jupiter. One planet orbits a pair of sunlike stars; the other circles two slightly smaller stars. The details of the discovery appear in the journal Nature. [William F. Welsh et al., "Transiting circumbinary planets Kepler 34 b and Kepler 35 b"]
Counting another planet unveiled last fall, the Kepler mission has now located three circumbinary worlds. The researchers estimate that millions of circumbinary planets similar to Kepler 34 b and 35 b must exist in the galaxy. Which means science fiction is once again becoming science fact.
—John Matson
[The above text is a transcript of this podcast.]
[Scientific American is part of Nature Publishing Group.]
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1 Comments
Add CommentSorry I can't afford the $32 charge to access the referenced research report, but its abstract opens with the statement:
Reply | Report Abuse | Link to this"Most Sun-like stars in the Galaxy reside in gravitationally bound pairs of stars (binaries)."
It concludes with the statement:
"The observed rate of circumbinary planets in our sample implies that more than ~1% of close binary stars have giant planets in nearly coplanar orbits, yielding a Galactic population of at least several million."
As for "...science fiction is once again becoming science fact", don't count on seeing any photographs of scenic multiple stars concurrently rising and setting in an alien sky any time soon.
It might be more likely that the Earth will be struck by some high velocity planet seemingly coming from nowhere.
Generally speaking, there is greater opportunity for planets orbiting a binary star pair to eventually be ejected than for planets orbiting a dominatingly massive single star. Please see:
http://en.wikipedia.org/wiki/Binary_star#Planets