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Kepler-16 b: (Almost) a Real-life Tatooine

Animation showing the circumbinary system, Kepler-16 b.
Richard Barkus, NASA-JPL/Caltech

A moody scene from “Star Wars” – Luke Skywalker watching a double sunset on his home world of Tatooine – seemed to gain a real-life analog with the announcement of a stunning discovery in 2011.

A planet dubbed Kepler-16 b, some 245 light-years from Earth, was found to orbit two stars. It was one of more than 2,700 confirmed exoplanets – planets beyond our solar system – credited to NASA’s Kepler Space Telescope, which retired in 2018 but still holds the record for most exoplanets found. The Kepler-16 double stars would appear in the sky of such a planet.

As so often happens in the collision of science and science fiction, the analogy isn’t quite what it seems. Kepler-16 b is a gas giant (not a giant desert), about the size of our own Saturn. That means no solid surface to stand on and gaze moodily at the double sunset.

Still, Kepler-16 b remains a rare and historic discovery. It is known as a “circumbinary” planet, tracing a wide orbit around a “binary” – two-star – system.

An observer on solid ground – say, on the surface of a hypothetical moon orbiting the planet – would indeed cast two shadows: a deeper one from the larger of the two stars, a somewhat fainter shadow from its smaller, reddish companion.

A “year” on Kepler-16 b, once around the star, would last 229 days, similar to our own system’s Venus at 225 days.

Only about a dozen of Kepler’s confirmed exoplanet discoveries are circumbinaries; the first to emerge out of data from TESS (the Transiting Exoplanet Survey Satellite), in 2019, was another gas giant called TOI-1338 b. The two stars in the circumbinary system found by TESS – Kepler’s successor and now NASA’s premier planet-hunter – are somewhat similar to the Kepler-16 stars: one larger, Sun-like star and one much smaller red dwarf.

‘Other Stars, Other Worlds’ — other stories

A retro looking travel poster for the exoplanet Kepler-16b shows a human standing on a rocky world with two suns large in the foreground. There is a larger white-yellowish sun, with a smaller orang sun. The person, seen from behind, has two criss-crossing shadows between an outcropping of rocks, reminiscent of the American Southwest. Like Luke Skywalker's planet "Tatooine" in Star Wars, Kepler-16b orbits a pair of stars. Kepler-16b is a gas giant, like Saturn, so it would have no solid surface to stand on. The view here is of and from an imagined nearby moon. Prospects for life on this unusual world aren't good, as it has a temperature similar to that of dry ice.

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