Closest star approach to the sun

Pair of stars buzzed the solar system 70,000 years ago

Scholz star

STELLAR FLYBY  A pair of dim red stars, shown in an illustration, passed within 0.8 light-years of the sun (left) roughly 70,000 years ago.

Michael Osadciw/Univ. of Rochester

Stars generally don’t rub shoulders with one another. Scholz’s star, however, is an exception. Roughly 70,000 years ago, the star — or, more precisely, the pair of stars orbiting each other — came within about 0.8 light-years of the sun. Our next-door neighbor star, Proxima Centauri, is more than five times that distance. The star flyby is the closest known.

Astronomer Eric Mamajek of the University of Rochester in New York and colleagues worked out the duo’s journey after measuring their current speed and direction. When the stars buzzed the solar system, they probably slipped inside the Oort cloud, a shell of trillions of comets hypothesized to envelop the solar system, the researchers report in the Feb. 10 Astrophysical Journal Letters.

Even during their closest approach, the stars (illustrated, with the sun in the distance at left) would have been invisible to the naked eye. One of the stars, however, occasionally flares. It’s possible, the researchers speculate, that humans at the time — some of whom were wandering out of Africa — could have seen Scholz’s star flicker into view for a few minutes or hours.

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