The Sun isn’t bothered by much. That’s because it travels through the Milky Way on its own. But most of the stars in the galaxy have at least one companion star. And the interactions between them can have a big impact.

Consider Spica, a bright star near the Moon tonight. Although it looks like a single star, it’s really at least two stars. One of them is more than 11 times the mass of the Sun, while the other is about seven times the Sun’s mass. That makes Spica one of the more impressive binary systems around.

The stars are extremely close together. They follow a stretched-out orbit that brings their surfaces to within about 10 million miles of each other.

So the stars have big effects on each other. For one thing, their mutual gravitational pull distorts both stars. They’re shaped like eggs, with the tapered end pointing toward the other star. Also, the pull of the smaller star appears to create ripples in the larger one. And the tapered end of each star is hotter than its opposite hemisphere.

In a few million years, the larger star will explode as a supernova. That’s likely to blast away some of the gas at the surface of the companion. And it’ll probably send the smaller star zipping across the galaxy – fired into space by a close companion.

Look for Spica to the right of the Moon early this evening. The fainter planet Mars is farther to the lower right of the Moon.

Script by Damond Benningfield