Moon and Spica

The two stars that make up Spica — the brightest star of Virgo — are monsters. Both are much bigger, brighter, and heavier than the Sun. That means they’ll have much shorter lifespans than the Sun. And the heavier of the two stars should end its life as a supernova — a titanic explosion that will rip it to bits.

But the fate of the second star isn’t quite as certain. It probably will end as a white dwarf — the same fate that awaits the Sun. But there’s a bit of wiggle room in the numbers. And that leaves the possibility that it, too, could become a supernova.

The main factor is the star’s mass. Most models of how stars work say that a star that’s at least eight times the mass of the Sun will expire as a supernova. And the smaller star of Spica — known as Spica B — appears to be a little more than seven times the Sun’s mass — below the line.

But there’s some wiggle room. Spica B could be right at eight times the Sun’s mass — just heavy enough to go “boom.” There’s also some wiggle room in the models — the lower limit of eight times the Sun’s mass isn’t a hard and fast number. And it’s hard to calculate how the other star will affect Spica B’s evolution. So while Spica B probably won’t light up the skies as a supernova, it’s not out of the question.

Look for Spica — the combined light of two monster stars — near the Moon tonight. It’s close to the lower right of the Moon as they climb into good view, by 10 or 10:30.
 

Script by Damond Benningfield