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Gamma Virginis

May 12, 2011

The constellation Virgo shines high in the south on spring evenings. Its brightest star, visible even from light-polluted cities, is Spica. But one of its most remarkable stars is less obvious.

To the eye alone, Gamma Virginis seems nothing special. But through a telescope, it's one of the most beautiful double stars in the sky.

The stars of Gamma Virginis are nearly identical in both brightness and color. Both are pale yellow, and are slightly larger, hotter, and brighter than our Sun. Astronomy author Robert Burnham Junior wrote that the two stars "look for all the world like the remote twin headlamps of some celestial auto, approaching from deep space."

The stars revolve around each other once every 170 years in a highly stretched-out orbit. Right now, they're pretty close together as seen from Earth, so you need a good-sized telescope to see them as individual stars.

This beautiful binary star is a close neighbor -- only 38 light-years away. So the light you see tonight actually left Gamma Virginis back in 1973.

Gamma Virginis has a much closer companion right now that can help you pick it out: the planet Saturn. It looks like a bright golden star high in the southern sky at nightfall, and is well to the left of the Moon this evening. Gamma Virginis is just a couple of degrees to Saturn's upper right -- the width of a finger held at arm's length.

We'll have more about the Moon and Saturn tomorrow.


Script by Ken Croswell


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