dipper@utastro.UUCP (Debbie Byrd) (06/26/85)
The moon is near the star Spica tonight. More about this star -- after this. June 26 Spica and the Moon If you look outside this evening, you'll see the moon near the star Spica in the constellation Virgo. Spica -- the 16th brightest star in the sky -- is supposed to represent an ear of wheat in the left hand of the virgin. Spica appears nearly lost in the bold light of the moon tonight. But this star shines over a distance of about 275 light-years, while the moon's light travels only a few seconds to reach our eyes. Spica is really two giant very luminous suns, whose centers are separated by only about 11 million miles -- much less than the distance between the Earth and our sun. The two stars that we see as Spica can't be split, or separated into two, through a telescope. We know there are two stars instead of one because of their spectra -- the rainbow band produced by shining starlight through a device similar to a prism. Each of the two stars in Spica is much more massive than our sun. One is about 10 times the sun's mass -- the other is about seven times as massive. Again, the two-in-one star that is Spica is located about 275 light-years away. The two orbit each other in such a way that they undergo shallow eclipses as seen from our vantagepoint in space. One star brushes in front of the top or bottom of the other -- and when that happens, the light from Spica dims minutely. So look outside tonight for the moon near the star Spica -- really two giant stars whirling around each other in only about four days. Script by Deborah Byrd. (c) Copyright 1984, 1985 McDonald Observatory, University of Texas at Austin