#Spica, the Bright Beacon of Virgo, is Two #Stars

The star Spica – aka Alpha Virginis – is the brightest #star in the #constellation Virgo the Maiden. From a distance of about 250 light-years, Spica appears to us on Earth as a lone bluish-white star in a quiet region of the sky. But Spica consists of two stars and maybe more. Both stars are larger and hotter than our Sun.

We say that Earth is 1 astronomical unit (aka 1 AU) from our sun. Spica’s two stars are only .12 AU from each other, a small fraction of the Earth-sun distance.

Spica’s two stars are so close, and they orbit so quickly around each other, that their mutual gravity distorts each star into an egg shape. It’s thought that the pointed ends of these egg-shaped stars face each other as they whirl around.

The pair of stars are both dwarfs, brightening near the end of their lifetimes.

Spica is one of the hottest 1st-magnitude stars. The hottest of the pair is 22,400 Kelvin (about 40,000 F or 22,000 C). That’s blistering in contrast to the Sun’s 5,800 Kelvin (about 10,000 F or 5,500 C). This star may someday explode as a supernova.

The light from Spica’s two stars, taken together, is on average more than 12,100 times brighter than our sun’s light. Their estimated diameters are 7.8 and 4 times our sun’s diameter.

How to find Spica

First, look for the Big Dipper in the northern sky. It’s highest in the evening sky in the northern spring and summer. Notice that the Big Dipper has a bowl and a long, curved handle. Follow the arc of the Dipper’s handle outward, away from the Dipper’s bowl. The first bright star you come to is orange Arcturus. Then "drive a spike" (or "speed on") along this curving path. And the next bright star you come to is Spica.