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ER Vulpeculae

September 27, 2013

Although we sometimes think of the Sun as a typical star, stars like our own are actually pretty rare. Only about one in 25 stars has a similar color, temperature, and luminosity as the Sun. Yet the constellation Vulpecula, the fox, boasts a remarkable system that consists of two stars that are almost identical to the Sun.

ER Vulpeculae is bright enough to see through binoculars. But no telescope on Earth or in space is good enough to show you the two stars separately — they’re so close together that their light blurs into a single pinpoint. Their surfaces are separated by only about a million miles, and the two stars whirl around each other once every 17 hours.

The stars spin just as fast as they orbit each other. That’s because their mutual gravitational pull creates strong tides that force the same side of each star to face the other, just as terrestrial tides force one side of the Moon to face Earth. So each star makes one full turn on its axis every 17 hours — far faster than the Sun, which rotates only about once a month.

The rapid rotation strengthens the stars’ magnetic fields, producing enormous spots and flares on both stars of ER Vulpeculae. The intense activity provides insight into what our own planet may have confronted billions of years ago. That’s because when the Sun was young, it too spun fast — and likely hurled huge flares that may have helped or hindered the development of life here on Earth.


Script by Ken Croswell, Copyright 2013

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