The Nearest Single Star To Earth Has Four Small Planets

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The nearest single star to the sun, Barnard's star, has a brood of planets all its own. The red dwarf star, about six light-years from Earth, hosts four close-in planets each about two to three times the mass of Mars, astronomers report in the March 20 Astrophysical Journal Letters .

"Barnard's star has a long history of claimed detections, but none of them could be confirmed for a long time," says astronomer Ritvik Basant of the University of Chicago. "It's pretty exciting to know what's orbiting the nearest stars."

From 2021 to 2023, Basant and his colleagues observed Barnard's star 112 times using the MAROON-X spectrograph on the Gemini North telescope in Hawaii. "I was starting to see these signals in the dataset," Basant says. But because he was still calibrating the instrument, "we ignored it for that time."

All four planets are so close to Barnard's star, which has about one-seventh the mass of the sun, that they orbit it in less than a week. That means they're too hot to be habitable, Basant says. In fact, the new observations probably rule out the presence of any habitable-zone planets.