Enter the Lion

Stealthily, like a great cat stalking its prey, the Lion of spring enters our sky. At sunset, shortly before 6:00. P.M., Orion and the stars of winter still hold center stage. But then, as Orion sinks towards the west, Leo and the stars of spring begin to appear in the east.

Most of the groupings of stars we call constellations have been seen differently in other lands and at other times; even the stars themselves have been grouped differently. But all men and women have seen a lion in these first stars of spring.

Almost directly overhead at chart time, you can recognize Leo by the sickle or backwards question mark that represents his great mane. His hind quarters stretch eastward almost to Virgo; he is seated and looks to the west. The inner stars of the Big Dipper point to the brightest star, or "lucida," of Leo. This is Regulus.

. Regulus is spinning much faster than the Sun and even faster than the Earth. The Sun rotates once a month: this means that a point on its equator travels four thousand miles an hour. Regulus, a star many times as big as the Sun, rotates in only sixteen hours. A point on its equator travels seven hundred thousand miles an hour. Any faster and the star would be ripped apart.

The result of this rapid spinning is that the star flattens out, and is a third wider than it is high. If there were any people living on a planet circling Regulus, they would look up and see, not a circular sun, but an oval.

There"s more: the axis of rotation of this star is in the direction of its motion away from us. Regulus is like a spinning bullet, speeding through space at almost ten thousand miles an hour.

(01/21/09)