Artist’s impression of a hot Jupiter orbiting close to a star. University of Warwick/Mark Garlick
Astronomers have located a planet similar to Jupiter that orbits its host star so closely that its year lasts just 18 hours. Planet NGTS-10b is 27 times closer to its star than Mercury is to the sun, and according to the researchers who discovered it, it is “perilously close” to being torn apart.
Located 1,000 light-years away from Earth, this is the shortest-ever orbital period discovered for this type of planet, called a hot Jupiter. The astronomers were able to locate the planet using what is called the transit method, in which they measure the brightness of distant stars and look for regular dips in brightness which indicate a planet is passing between the star and Earth.
“Although in theory hot Jupiters with short orbital periods (less than 24 hours) are the easiest to detect due to their large size and frequent transits, they have proven to be extremely rare,” lead author Dr. James McCormac from the University of Warwick Department of Physics said in a statement. “Of the hundreds of hot Jupiters currently known there are only seven that have an orbital period of less than one day.”
The planet is also tidally locked, which means one side of it always faces toward its star. This contributes to blistering surface temperatures which are estimated to be more than 1,000 degrees Celsius.
The astronomers are curious as to how the planet came to be located so close to a star, and they assume it must have formed elsewhere and migrated inward. “It’s thought that these ultra-short planets migrate in from the outer reaches of their solar systems and are eventually consumed or disrupted by the star,” co-author Dr. David Brown explained. “We are either very lucky to catch them in this short period orbit, or the processes by which the planet migrates into the star are less efficient than we imagine, in which case it can live in this configuration for a longer period of time.”
The long-term outlook for the hot planet is not looking good, as the researchers believe it will eventually be destroyed. “Over the next ten years, it might be possible to see this planet spiraling in,” co-author Dr. Daniel Bayliss said. “The best model that we’ve got suggests that the star is about ten billion years old and we’d assume that the planet is too. Either we are seeing it in the last stages of its life, or somehow it’s able to live here longer than it should.”