The planet KELT-4Ab shouldn’t exist. This alien world is a ‘hot Jupiter’ – a huge gas planet that orbits closer to its parent planet than Mercury does to our Sun. Not only that, but it has three suns – an incredibly rare and thrilling discovery. Astronomers hope that KELT-4Ab may provide crucial clues as to how hot Jupiter planets exist at all.
The KELT-4 system was first investigated in 1973, but back then astronomers thought only two suns were present. Now many decades later, researchers used robotic telescopes and discovered that one of those stars is actually two stars that orbit each another. These two stars are close enough to KELT-4Ab that they look like two full moons on its horizon.
Hot Jupiters have baffled astronomers for some time now. The planets formed far away from their parent suns, as our Jupiter did, but then they migrated much closer to their parent suns. Before we were able to observe other solar systems, scientists posited that all large gas giants formed and stayed in place as Jupiter did. The presence of hot Jupiters shatters that theory.
Lead author on the study Jason Eastman said, “Hot Jupiters aren’t supposed to exist. None of them. 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 KELT-4 system is only 680 light-years away from Earth, and the relatively close distance will allow astronomers to probe the system further for potential answers. The Gaia satellite, operated by the European Space Agency, will study the system and measure the orbiting paths of the three suns. These measurements may provide insight into how KELT-BC could have interacted with KELT-4Ab to propel it closer to the parent star, which could have implications for why hot Jupiters are present in the universe.