If this planet were real, it would be weirder than Tatooine

Back in 2016, scientists thought they'd come across a planet hanging out with three suns. Turns out that was wrong.

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Editors' note: On April 14, 2022, nearly six years after this story originally appeared, the research paper on the discovery of  HD 131399Ab was retracted. More recent observations have revealed that what looked like a planet was really an object in the background, probably a star that's light-years away. You can read our story on that here. In the interests of transparency, we are leaving the original story below as it appeared on July 7, 2016.

Luke Skywalker's home planet in Star Wars has two suns, and wherever Westeros from "Game of Thrones" is, it suffers from long and weirdly unpredictable winters, but a real exoplanet over 300 light-years away may be even more strange. Astronomers have found the first planet orbiting three suns, giving it quite a lot of sunrises, sunsets and daylight depending on the seasons, which last for centuries.

Enlarge Image

Artist's impression of HD 131399.

ESO/L. Calçada

The gas giant HD 131399Ab is located 340 light-years from here in the constellation Centaurus, where it is part of an odd three-star system. The planet orbits closely to the brightest of the three stars, while the other two stars whirl about each other in a hyperactive dance as the pair orbits the brightest star.

If you were standing on the planet, which would be difficult because it's very hot and mostly gas, your daily interaction with your three stars would be pretty different from what we're used to from our plain old single sun.

"For about half of the planet's orbit, which lasts 550 Earth-years, three stars are visible in the sky, the fainter two always much closer together, and changing in apparent separation from the brightest star throughout the year," said Kevin Wagner, a member of the research team that discovered the planet, in a release.

"For much of the planet's year the stars appear close together, giving it a familiar night-side and day-side with a unique triple-sunset and sunrise each day," he continued. "As the planet orbits and the stars grow further apart each day, they reach a point where the setting of one coincides with the rising of the other -- at which point the planet is in near-constant daytime for about one-quarter of its orbit, or roughly 140 Earth-years."

You can get a better idea of what the system looks like in the video below. Good luck to anyone tasked with coming up with a calendar for this planet.

I asked Wagner during the team's Reddit "Ask Me Anything" session if we could say this planet might have weather kind of like the opposite of Westeros on "Game of Thrones": really long and brutal summers (rather than winters) that arrive every few centuries.

"Probably not, the planet is about twice as far from its nearest star as Pluto is from our sun, and even further from the other stars," Wagner explained. "Although it experiences nearly constant daylight during its summer season, it still doesn't receive very much starlight. However, the planet is still very hot from its formation -- the surface that we see is over 1,000 degrees Fahrenheit, and even hotter at lower layers, and that's lasted for the planet's ~16 million-year lifetime!"

Looks like there's still no known explanation in our universe for the meteorological quirks borne out of George R.R. Martin's head.

The discovery was the first made with Sphere, which stands for the Spectro-Polarimetric High-Contrast Exoplanet Research Instrument, a tool that's part of the Very Large Telescope operated by the European Southern Observatory in the Atacama Desert of northern Chile. Sphere is particularly good at detecting infrared light like that coming off young, hot planets like this one.

A full paper on the discovery came out online in the journal Science Thursday.