How Did We Miss This Enormous, Jupiter-Like Gas Planet and It's the Size of 3 Damn Suns?

Big news, space nerds: Scientists at the Harvard-Smithsonian Center for Astrophysics have identified a Jupiter-scale planet with three whole suns to its name. That's a big and unusual find. So why didn't we see it sooner?

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Well, we did — we just thought the so-called hot Jupiter lived in a binary solar system. As it turns out, the KELT-4 system houses three stars and one gas planet; two of those stars, KELT-4B and KELT-4C, sit far away from the action and were previously thought to be one star. According to the Washington Post, they require 4,000 years to make the trip around the system's main star, KELT-4A, and thirty years to circle one another. This hulking planet, KELT-4Ab, by contrast, makes its tour of KELT-4A in three days.

What we have here is a situation in which KELT-4Ab orbits KELT-4A, and KELT-4B and -4C circle each other off to the side — quite far off to the side. Which is bound to sound wonky to many readers, but actually makes sense when one considers what a hot planet Jupiter actually is.

As planetary science professor Heather Knutson explained on Universe Today, these extrasolar planets — meaning "planets that orbit stars other than the sun," but "in the same part of our own corner of our galaxy" — circle their suns at a much tighter range than even Mercury circles ours. They are, Knutson said, "absolutely getting roasted," which is why hot Jupiters are alternatively called roaster planets. 

"We know that they couldn't have formed there — they had to have formed farther out and migrated in, so what we're still trying to understand are what are the forces that caused them to migrate in," Knutson said. What caused this particular gaseous giant to migrate, according to the Post, may just have been lurking binary stars KELT-4B and -4C. 

"Gaseous planets the size of Jupiter are supposed to form much farther out [from their parent star] and stay there, like our own Jupiter did," the study's lead author Jason Eastman told Space.com. "Exactly how they got so close is an outstanding question, but one theory is that it migrates due to hot interactions with a third body — in this case, the third and fourth bodies KELT-BC."

In other words, researchers believe that the KELT-4 system's hot Jupiter was sort of herded over to its sun by the pair of smaller stars.

According to Space.com, such a triple star situation is rare — but not enormously so. Eastman and his teammates spotted this one (some 40 years after KELT-4's initial discovery in 1973) because the cosmic triad sits so close to Earth, he told Space.com. They hope this system will shine some light on the movements of other such hot Jupiters that snuggle uncomfortably close to their stars' sides.