One of the things that seems very weird in Star Wars is the planet Tatooine, which has two suns. Binary suns? How could a planet revolve around two suns? The most logical explanation is that the planet moves orbitally in the same plane, or disk, that the suns use to revolve around each other. Binary stars have been found in the Milky Way galaxy, some with planetary discs in their revolutionary plane, but others are much stranger. Some revolve perpendicular to their planetary disks, and one system has four stars!
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The stars in the binary system Ea and Eb are both low mass, about 0.93 and 0.28 times the mass of the Sun. They orbit each other in just 19 days on a mildly elliptical orbit, and are surrounded by a lovely disk of gas and dust about 4 billion kilometers in radius (a disk that orbits both stars in a binary like that is called a circumbinary disk).
Careful examination of the data showed that the plane of the stars’ orbits and the plane of the disk match to within a few degrees. In fact, looking at other short-period binaries they found the same thing.
But when they looked at binary stars that orbit farther out, the disk is highly tilted. An earlier paper from a different team of astronomers, for example, looked at a different young system, called HD 98800. This too is what’s called a hierarchical quadruple system, with two pairs of binary stars orbiting each other. The inner pair (HD 98800 Ba and Bb) has a ring of dust surrounding it, but that ring is perpendicular to the binary orbital plane. The orbital period of that binary is 315 days, much longer than UZ Tau E. Again, the same is true for several other system they examined.
But back to Tattoine, which is more mundane than we realized in 1977. If the planet’s revolution is circumbinary, its residents would see a solar eclipse about every day (although they shouldn’t look at it). Read about both real and fictional binary and multiple star systems at Bad Astronomy.
(Image credit: Disney/Lucasfilm)
Source: neatorama