Moon and Regulus

The bright heart of the lion beats near the Moon this evening. Regulus, the star that marks the heart of Leo, stands quite close to the lower left of the Moon at nightfall.

And Regulus is a strong heart. It’s much bigger, brighter, and more massive than the Sun. And it spins about 15 times faster — more than 700,000 miles per hour at the equator.

Regulus whirls around so fast because it “stole” a lot of gas from a nearby companion star. As the gas poured in, Regulus twirled faster and faster. Today, it spins so fast that it bulges outward at the equator, so it looks like a smashed beachball.

If Regulus were to spin just 10 percent faster, it would rip itself apart. That’s unlikely to happen — for one thing, it’s already pulled in all of the available gas from its companion.

But some other stars are seen to spin much closer to that edge. Gas squirts away from such a star’s equator, forming a disk around it.

As the gas moves out, it can come together to form tiny grains of dust. The stardust absorbs some of the star’s light — especially blue light. That can make the star look much redder than it really is. In the 1800s, for example, astronomer John Russell Hind watched as one star changed from red to blue in a matter of weeks. The most likely explanation is that the star had spun off a shell of gas and dust, making it look red. The shell soon dissipated, though, allowing the star’s true color to shine through.
 

Script by Damond Benningfield