Distant planet has three suns and a year more than 500 times longer than ours

L. Calçada/ESO

Distant planet has three suns and a year more than 500 times longer than ours

Far-off solar systems keep getting weirder: Researchers have spotted a super-Jupiter orbiting a star in a three-sun system at a distance twice as far as Pluto is from our own sun. That makes the planet, dubbed HD 131399Ab (lower left in this artist’s representation), by far the widest ranging exoplanet in a multistar system, the scientists report online today in Science. Preliminary data suggest that the gas giant—about four times the mass of Jupiter—orbits the largest and brightest of the three stars (which has about 1.8 times the mass of our sun) once every 550 years or so. The other two suns in the system (depicted in the background at right), smaller stars that orbit each other relatively tightly and quickly, lie somewhere between 45 billion and 60 billion kilometers away. The intricate dance of the planet and these stars (seen in this video) is taking place about 320 light-years from us. Measurements at near-infrared wavelengths suggest that HD 131399Ab’s atmosphere contains water vapor and methane, and that the planet’s cloud tops are about 850 K (577°C). It’s not exactly clear where this odd world formed, the team notes: It might have coalesced closer to the main star in the system and then migrated outward to its present locale, or it may have formed in orbit around the smaller pair of stars only to be ejected and then captured by the larger star.