Moon and Spica

StarDate

In most star systems, Spica B would be a monster. It’s about seven times the mass of the Sun, and more than 2,000 times brighter. Its heft puts it in the top one-tenth of one percent of all the stars in the Milky Way Galaxy.

But Spica B has a companion that’s far more impressive. Spica A is more than 10 times the Sun’s mass, and 20 thousand times its brightness. And it has a more impressive fate: It’ll explode as a supernova.

On the other hand, Spica B will live tens of millions of years longer than Spica A. That’s because of the difference in mass. Heavier stars burn through their nuclear fuel more quickly; the heavier the star, the faster and hotter it burns. So while Spica A is quite young, it’s already completed the “prime” phase of life. Now, it’s getting bigger and brighter as it approaches the end.

After Spica A explodes, Spica B will still have another 60 million years or so left. Even so, its lifetime will be quite short – about 10 billion years less than the Sun. And when its time is up, it probably won’t explode. Instead, it’ll cast off its outer layers in a less-violent process. That will leave only its hot but tiny core, shining faintly for many billions of years to come.

Look for the Spica system quite close to the Moon as darkness falls. It looks like a single point of light. The planet Venus – the brilliant “evening star” – stands to their lower right.

Script by Damond Benningfield