Your Earth Is Exotic, But Did You Hear About This Planet With 3 Suns?

There is one planet that is 120 light years away in the Centaurus constellation. If that doesn't really make you avid to drop into it, then listen to more. It is four times bigger than Jupiter and orbits twice as far out as Pluto. Strangest of all is that it has three suns!

At the European Southern Observatory's Very Large Telescope, a team of astronomers found a planet in the far-out triple star system. This is just the second such exoplanet familiar to us. This is planet HD 131399Ab, which is gravitationally influenced by the triple suns. It has not been clear whether such a planet could live on or not.

"I'd venture to say this is the weirdest orbit of any exoplanet we've ever found," Kevin Wagner, an astronomer at the University of Arizona and lead author of the study said. "We know of no other planet in a configuration like this."

Astronomers have found thousands of exoplanets by transit photometry. Yet, just a few of them have been imaged directly.

"We report the discovery via imaging of a young Jovian planet in a triple star system and characterize its atmospheric properties through near-infrared spectroscopy. The semi-major axis of the planet is closer relative to that of its hierarchical triple star system than for any known exoplanet within a stellar binary or triple, making HD 131399 dynamically unlike any other known system," explains sciencemag.

HD 131399A orbits a young A-type star, HD 131399A. One rotation takes 550 Earth years to finish. And far beyond this orbit, a Sun-like star and a K-dwarf are "twirling about one another just like dumbbells," even as they are rotating around another star.

"The planet is about a third of a way out [between star A, and the B/C pair]," Wagner said. "All of the stars have a lot of gravitational influence on the planet, meaning it has a very irregular orbit that's constantly evolving and changing."

Will this gravitational three-star arrangement rip it apart and push it out from its birthplace? It is not known. Although HD 131399Ab is a small planet that is only 16 million years old, it has managed to survive.

"We thought that [triple star planets] weren't going to be common, or at least in this extreme configuration, so we hadn't really looked," Wagner said. Studying these systems will expand our understanding of the conditions under which planets form and migrate about.

"I like to start thinking about it from when the planet is opposite all three stars," Wagner said. "When they aren't eclipsing, you'd see three suns in the sky. As the planet progresses in its orbit, the stars will start to grow apart, to the point where the setting of one coincides with the rising of another."

Hence, there are two seasons presumed here---one with three sunrises and sunsets every day, or perhaps one with "perpetual daylight, where a rising star (or stellar pair) is always there to replace a setting one."

Doesn't that sound like a great vacation hotspot?