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Close Encounters

November 1, 2017

The star Gliese 710 is so faint that it’s invisible to the eye alone. In 1.3 million years, though, it’ll be the brightest star in the night sky, as it passes about a quarter of a light-year away.

The encounter could be deadly: The star could deflect some of the icy bodies that surround the Sun, sending them toward the inner solar system, where they could smack into Earth.

Researchers reached that conclusion when they combined older data with the first 14 months of observations by Gaia, a European satellite that’s plotting the distances to a billion stars in the Milky Way galaxy. The study found that Gliese 710’s encounter will be roughly one-third the distance of previous estimates — the closest of any star in the next five million years.

During that span, up to 600 stars will pass within 16 light-years of Earth, with up to two dozen passing within three light-years. The gravity of any of these stars could stir up the Oort Cloud, a shell of icy bodies that forms the outer edge of the solar system. When such bodies enter the inner solar system they form comets, with long, glowing tails. If a comet strikes Earth it can decimate life. In fact, that probably happened about 65 million years ago, when an impact by a comet or asteroid helped bring about the demise of the dinosaurs.

More observations by Gaia should allow astronomers to refine the new estimates, and extend the projections of encounters to 25 million years into the future.


Script by Damond Benningfield

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