A newly found planet, called KELT-4Ab, has been discovered to be a triple-star system. While two star planets, called circumbinary planets, are common, KELT-4Ab is only one of four planets to have three suns.
The gas giant KELT-4Ab orbits one star — called KELT-A — every three days, while the other two stars — KELT-B and C — complete an orbit around each another approximately every 30 years. The two stars also form a binary system, which is much farther away, and makes one orbit around KELT-A around every 4,000 years.
KELT-4Ab is about as enormous as Jupiter, and is located in a very peculiar star system nearly 700 light-years away. Because of its close proximity it may give better insights into how gas giants that sit close to their parent star — known as “hot Jupiters” — evolve.
KELT-A is brighter than the other two stars; not only is it a hotter star, it also lies much closer to Earth — only 680 light-years away. Standing on the surface, well standing in KELT-4Ab atmosphere since you can’t actually stand on its surface, KELT-A would appear around 40 times as large as the sun appears here on Earth due to its close proximity.
KELT-B and C would appear much dimmer due to their great distance, shining no brighter than our full moon.
Although scientists have known of the existence of the KELT system for several years, it was always thought that the binary stars were just one star. By using the Kilodegree Extremely Little Telescope (KELT) — which is how the KELT system got its name — researchers were able to see that they were actually a binary system.
The triple-star system now offers a unique opportunity for scientists to gain insight into how gas giants, like KELT-4Ab, manage to orbit so close to their star. Current theory suggests that they should be more distant, as with Jupiter. However, one possibility for this new discovery is the nearby binary system may have something to do with it.
Jason Eastman, a research associate at the Harvard-Smithsonian Center for Astrophysics, and is the lead author of a study, told Space.com:
“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.
“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 binary system KELT-4BC may be what ultimately drove the planet KELT-4Ab so close to its star.”
The researchers working at the Harvard-Smithsonian Center for Astrophysics have published their findings in The Astronomical Journal.