Moon and the Sickle

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Moon and the Sickle

A bit of danger looms above the crescent Moon this evening: a sickle. It’s a curved pattern of stars that forms the head, mane, and heart of Leo, the lion. The handle is Regulus, the lion’s heart, to the left of the Moon. And Leo’s next-brightest star is near the middle of the sickle — looming above the Moon.

Algieba is a binary — two stars locked in orbit around each other. The system is about 130 light-years away. By astronomical standards, that’s nothing more than a hop. And the two stars are separated by about four times the distance between the Sun and Pluto.

Even so, the system still isn’t all that well understood. Astronomers know that both stars are into their final phase of life. They’ve used up the original hydrogen fuel in their cores, which has caused them to swell up. So both stars are a good bit bigger and brighter than the Sun.

Estimates for one star say it’s about 30 times wider than the Sun, although it could be even bigger. The size of the other star is even less well known — astronomers can only make a rough guess.

We do know that the better-known star has a planet. It’s about nine times the mass of Jupiter, the giant of our own solar system. It’s just a little bit farther out than Earth is from the Sun. There’s evidence of a second planet much farther out. But so far, that’s unconfirmed — one more thing to learn about a bright star system in the sickle.

Script by Damond Benningfield

Today's program was made possible by Mercer Caverns, in Calaveras County in California's historic Gold Country.

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