Moon and Spica

A star system with an explosive future stands to the lower right of the Moon early tomorrow. One of the system’s two known stars is massive enough to end its life as a supernova.

Spica is the leading light of the constellation Virgo. It’s only about 250 light-years away. That makes it the closest supernova candidate in its category.

That category is known as a “Type 2” supernova. Such a blast occurs when a massive star reaches the end of its life. Its core can no longer produce nuclear reactions. Without the energy from those reactions to push against the pull of gravity, the core collapses. The surrounding layers of gas fall inward, then rebound — blasting themselves to bits. For a while, the explosion can outshine billions of “normal” stars.

And that’s the likely fate of the heavier of Spica’s two stars. It’s more than 11 times the mass of the Sun — well above the limit for becoming a supernova. And it’s already gone past the end of its “normal” lifetime, so the clock is ticking toward its demise.

The future is a bit hard to see, though, because of the second star in the system. The two stars are extremely close together. Over the next few million years, the heavier star will get much bigger. Eventually, it will engulf its companion. Just how that’ll affect the evolution of the two stars is uncertain. But it’s unlikely to prevent the fireworks from Spica’s massive star.

We’ll talk about the Moon and some other dawn companions tomorrow.

Script by Damond Benningfield