Circumbinary Planet

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Circumbinary Planet

Astronomers have discovered dozens of planets that orbit both stars in a binary system. Like Tatooine of “Star Wars” fame, that gives the planets double sunrises and sunsets. But only a handful of those planets lie in their system’s “habitable zone” — the region around the stars that are most comfortable for life. That means we haven’t yet seen a real Tatooine just yet.

One of the circumbinary systems is close to the Northern Cross — the body and wings of Cygnus, the swan — which is nosediving into the northwestern horizon at sunset. The system is just off the end of the right arm of the cross. But it’s so faint that you need a telescope to see it.

The system is known as Kepler-47. It’s more than 3,000 light-years away. And it’s perhaps the most Tatooine-like system yet seen. Its main star is about as big and as bright as the Sun. The second star is a bit smaller and a good bit fainter. The planet orbits them once every 10 months, at an average distance that’s about the same as Earth to the Sun.

The planet itself is a bit more than three times the mass of Earth, and about five times Earth’s diameter. That means it’s probably half gas and half rock and ice. That composition isn’t especially good for hosting life. But the planet could have good-sized moons, where conditions could be more comfortable. So while Kepler-47c might not be Tatooine, one of its moons could be.

Script by Damond Benningfield

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