A year on this exoplanet only takes 18 hours. And it might be doomed

Every 18 hours, a newly discovered exoplanet found 2,000 light-years away from Earth completes an orbit around its star — and potentially takes another step closer to being ripped apart.

The exoplanet, known as NGTS-10b, is considered to be a “hot Jupiter” — a type of gas giant exoplanet that is 20% bigger than Jupiter and twice its mass. (An exoplanet is any planet found orbiting a star outside of our solar system.)

Astronomers found the exoplanet with the Next-Generation Transit Survey, a telescope collaboration at the European Southern Observatory’s Paranal Observatory in Chile. They used the transit method, which involves observing stars and noting dips in their brightness as evidence for planets orbiting them. This particular exoplanet’s star was one out of 100,000 that caught their attention due to the frequent dips they observed.

The star is similar to our sun, but it’s 1,000 degrees cooler. The exoplanet orbits it about 27 times closer than Mercury to our own sun, which is why it only takes 18 hours to complete an orbit. It’s also tidally locked, which means that one side of the planet perpetually faces the star and reaches about 1,832 degrees Fahrenheit on the surface.

Details about the new exoplanet published this week in the Monthly Notices of the Royal Astronomical Society journal.

“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,” said James McCormac, lead study author from the University of Warwick Department of Physics. “Of the hundreds of hot Jupiters currently known, there are only seven that have an orbital period of less than one day.”

Based on the theory of planet formation, large planets like this one typically form distant from their star and move closer in over time. The astronomers want to continue observing this exoplanet in the future to determine if its orbit is stable or if it will crash into the star. If its orbit spirals any closer, the two will engage in a death dance that will lead to the planet’s end. Although technically, we’d be witnessing the end of a planet a thousand years in the past, given its distance from Earth.

“Over the next ten years, it might be possible to see this planet spiraling in,” said Daniel Bayliss, study co-author at the University of Warwick’s Centre for Exoplanets and Habitability. “We’ll be able to use NGTS to monitor this over a decade. If we could see the orbital period start to decrease and the planet start to spiral in, that would tell us a lot about the structure of the planet that we don’t know yet.”

Finding the planet now gives astronomers the opportunity to observe it over time and possibly fill in the gaps of what we know about hot Jupiters.

“Everything that we know about planet formation tells us that planets and stars form at the same time,” Bayliss said. “The best model that we’ve got suggests that the star is about 10 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.”