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Wolf 359

March 7, 2018

In March of 1918, German astronomer Max Wolf spotted a fast-moving star in the constellation Leo, the lion. Its quick motion across the sky suggested that it’s quite close to Earth. And follow-up observations confirmed that it is — it’s just 7.8 light-years away. Yet Wolf 359 is so faint that you need a telescope to see it.

At the time of its discovery, in fact, Wolf 359 was the most feeble star known. It takes more than a century for it to radiate as much visible light as the Sun emits in just one day.

The star is a red dwarf, which means it’s little, faint, and cool. Today, we know that red dwarfs are the most common type of star in the entire galaxy. In fact, they outnumber all the other types of stars put together. But they’re so faint that not a single one is visible to the unaided eye.

Wolf 359 was the last of three nearby red dwarfs discovered during the 19-teens. The first, found in 1915, was Proxima Centauri, which turned out to be our closest neighboring star. The following year, American astronomer Edward Emerson Barnard discovered a red dwarf that now bears his name. It’s a little farther than Proxima Centauri, but a little closer than Wolf 359.

Wolf 359 emits less light than either of the others. For decades, in fact, it held the distinction of being the most feeble star known — a puny cosmic ember that was discovered 100 years ago this month.

Script by Ken Croswell

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