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Van Biesbroeck's Star

July 16, 2011

The evening skies of summer feature Aquila, the eagle, whose brightest star, Altair, is easy to see. But the constellation also hosts a much more modest star, named for a modest man. For four decades, the star was the faintest known.

The star is named for George Van Biesbroeck, who was born in Belgium in 1880 and came to the United States in 1915. He studied binary stars -- two stars that orbit each other -- and worked at Yerkes Observatory in Wisconsin, whose 40-inch telescope was ideal for his work.

In the 1930s, the University of Texas built McDonald Observatory, with Yerkes overseeing its operation. Van Biesbroeck helped supervise the observatory's construction, and used its new 82-inch telescope to search stars near the Sun for faint companions. In late 1943, he spotted a dim star beside a red dwarf in Aquila. Red dwarfs are small, cool stars, but they outnumber all other stars put together.

Van Biesbroeck's Star was a red dwarf, too, but was even punier than the average red dwarf. As Van Biesbroeck noted, the star generated so little light that if it replaced the Sun, it would look only about as bright as the full Moon.

Van Biesbroeck died in the 1970s. His star retained its place as the faintest known until the 1980s. Van Biesbroeck's star remains a close neighbor, though -- it's just 19 light-years away -- only two light-years farther than Altair.


Script by Ken Croswell, Copyright 2011


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