Moon and Spica

StarDate

This might come as a bit of a surprise, but no star is perfectly round. A star’s rotation, and the gravitational tug of any companion stars, can distort the shape. So most stars are slightly flattened. The Sun, for example, is about six miles wider through the equator than through the poles. The Sun’s average diameter is about 865 thousand miles, though, so that slight flattening isn’t noticeable. But some stars are so squashed that they look like lozenges. And still others look like eggs.

Two egg-shaped stars form the system known as Spica, the leading light of the constellation Virgo.

Both of Spica’s stars are much bigger, brighter, and heavier than the Sun. And the stars are quite close together. Their surfaces are just a few million miles apart — so close that we can’t see them as individual stars even through the largest telescopes.

Because the stars are so big, their grip on their outer layers of gas is pretty weak. And at their tight range, the gravity of each star exerts a pretty good pull on the other. That distorts the shapes of both stars — it makes them “bulge” outward. So if we could see the system up close, both stars would look like eggs, with the narrow ends pointing toward each other.

Look for Spica close to the left or lower left of the Moon as darkness falls this evening. The bright star will stand about the same distance to the right of the Moon tomorrow night.

Script by Damond Benningfield