Spica: Alpha Star of 'Lizard Lady'

The moon is full at week’s start, so expect to see only the brightest stars and planets.  Venus has now become the sole guardian of evening twilight.  View it about 30 minutes after sundown in the same direction where the “sun goes down” low in the WNW.  

If you look just a little bit west of south at 10 p.m., you’ll notice two very bright luminaries; the one to the left is Saturn. To Saturn’s right will be Spica, the alpha star of Virgo the Virgin.  Although Virgo is one of the zodiacal constellations through which the sun passes, its star pattern is only discernable under the clearest of skies because of the faintness of the other stars which form the constellation.  She looks more like a “lizard lady” in a sleeping bag, and I can understand fully why suitors have been reluctant to call. 

Blue-white Spica, however, is a whole different story. It is truly one of the more luminous stars in the heavens, but because of its 250-light year distance, it appears as only the 16th brightest star of the night.  

However, if Spica were moved to 10 parsecs or 32.6 light years from our sun, the standard distance to which the brilliance of all stars are compared, Spica would rival the planet Venus in luster. 

In contrast, Sol would be an inconspicuous star, even from rural locations, similar to the other faint stars which form Virgo, the “Lizard Lady’s” body.  

Spica is, at the very least, a double star system with two hot, blue-white luminaries orbiting each other in just over four days. Their separation is a mere 11 million miles, about 1/8th the Earth-sun distance.  

The brighter component of the pair has a surface temperature of 40,800 degrees F, while its fainter companion is just 7000 degrees cooler.  

The temperature of our sun, in comparison, is only 10,500 degrees F.  

Catch Spica now; for in the weeks ahead, it will continue to slide towards the western horizon, exiting the deep twilight sky by late August. 

© Gary A. Becker—www.astronomy.org

Moravian College Astronomy