Moon and Spica

Planets are everywhere. Astronomers have discovered more than 4,000 confirmed planets in star systems other than our own. And the list is likely to grow by thousands more in the years ahead.

One system where we’re not likely to find planets is Spica, the brightest star of Virgo. It’s well to the right of the Moon at first light tomorrow.

Spica is a binary — two stars that are bound to each other by their gravity. The surfaces of the two stars are only a few million miles apart. With such a small gap between them, no planet could orbit either star individually.

Astronomers have discovered planets in other binaries that orbit both stars in the system. But that’s less likely to be the case for Spica.

The surfaces of both of Spica’s stars are tens of thousands of degrees hotter than the Sun. They would vaporize any solid bits of ice or rock anywhere near the stars. And strong “winds” from the stars would blow these planet-making materials far away. So if any planets have formed at Spica, they would have to be many times farther out than Earth is from the Sun. Such worlds would be extremely hard to find with current techniques.

And even if Spica does have planets, they probably wouldn’t last for long. The heavier of Spica’s two stars probably will explode as a supernova. Planets aren’t strong enough to withstand the radiation and shockwave from such a blast. So if planets orbit Spica, they’ll live short lives — and die violent deaths.

Script by Damond Benningfield