Astrophysicists have discovered a distant planet that has not one, not two, but three suns in its sky. While the Jupiter-sized world, named KELT-4Ab, orbits a single star (KELT-A), its system is within close proximity of a binary star, containing KELT-B and KELT-C, which circle each other as part of a larger orbit around KELT-A. Every 4,000 years or so, KELTs A, B, and C fall adjacent to each other and are all visible together in KELT-4Ab’s sky.
The phenomenon was discovered by Research Associate at the Harvard-Smithsonian Center for Astrophysics Jason Eastman, who is the lead author of study on KELT-4Ab, which used the Kilodegree Extremely Little Telescope – two robotic telescopes in Arizona and South Africa, and the origin of the KELT moniker – to observe the curious planet and stars.
“Those two stars would orbit each other every about 30 years, and every 4,000 years they’d make one orbit around KELT-4A,” Eastman told Space.com.
In addition to its three suns, though, KELT-4Ab is curious for another reason: it is a type of planet known as a “hot Jupiter”, which is a gas giant that is positioned close to a sun, an occurrence that, theoretically, cannot yet be explained.
“Hot Jupiters aren’t supposed to exist. None of them,” Eastman said. “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,” he said. “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.”
The two unusual discoveries – the three stars and the “hot Jupiter – may even be related, according to Eastman. “The binary system KELT-4BC may be what ultimately drove the planet KELT-4Ab so close to its star,” he said.