New Exoplanet Circles Star in Less Than 9 Hours (and Is Covered by Molten Lava)

This artist illustration shows the newly discovered exoplanet Kepler 78b orbiting so close to its parent star that a single year lasts only 8.5 hours. Credit: Cristina Sanchis Ojeda

NASA’s Kepler Space Telescope has helped discover a new Earth-sized planet that has a year that lasts less time than an average work day or a good night’s sleep.

Kepler 78b zips around its host star in a mere 8.5 hours — making this one of the shortest orbital periods ever detected. (See also: “Most Earthlike Planets Found Yet: A ‘Breakthrough.'”)

Researchers at MIT are reporting that Kepler 78b sits about 700 light years away from Earth, and orbits about 40 times closer to its parent star than Mercury does.  This scorched planet orbits so close  that it sports temperatures reaching up to 5,000 degrees Fahrenheit.

While this would seem to be the destination to celebrate a lot of birthdays it’s probably not the best place for a vacation since scientists predict the surface is covered with molten lava.

“We’ve gotten used to planets having orbits of a few days,” said Josh Winn, co-author of both studies in a press statement.

“But we wondered, what about a few hours? Is that even possible? And sure enough, there are some out there.”

Winn and his team were able to detect the light given off by Kepler 78b by measuring the dips in starlight each time the planet periodically passed in front of its star. (Related: Kepler Spacecraft Disabled; “Exciting Discoveries” Still to Come)

Looking forward, Winn will be working towards getting a handle on how much this planet may actually tug on its star, which will hopefully allow the team to measure the planet’s mass, making it the first Earth-sized planet outside our own solar system whose mass is known.

But the discovery of this hellish planet doesn’t rule out the possibility that there may be other short-period alien worlds out there that are indeed habitable. Winn’s team is on the hunt now for just these kind of planets circling small brown dwarf stars.

“If you’re around one of those brown dwarfs, then you can get as close in as just a few days,” explained Winn. “It would still be habitable, at the right temperature.”

The discovery of Kepler 78b appears in The Astrophysical Journal.

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Meet the Author
Andrew Fazekas, aka The Night Sky Guy, is a science writer, broadcaster, and lecturer who loves to share his passion for the wonders of the universe through all media. He is a regular contributor to National Geographic News and is the national cosmic correspondent for Canada’s Weather Network TV channel, space columnist for CBC Radio network, and a consultant for the Canadian Space Agency. As a member of the Royal Astronomical Society of Canada, Andrew has been observing the heavens from Montreal for over a quarter century and has never met a clear night sky he didn’t like.