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Moon and Regulus

July 11, 2013

Regulus, the bright heart of Leo, the lion, shines close to the upper right of the crescent Moon as night falls this evening. Venus, the brilliant “evening star,” is farther to the Moon’s lower right.

The name “Regulus” means “the little king.” Yet it’s not so much a monarch as a ruling quartet. That’s because Regulus appears to consist of not one star, but four.

Only one of them is bright enough to see with the unaided eye — the one we know as Regulus. But it has a close companion that once shined even brighter than Regulus itself.

This companion was bigger and heavier than Regulus, so it aged more quickly. As it neared the end of its life, it puffed up. Much of its outer layers of gas poured over onto Regulus, making it bigger and brighter, and making it spin much faster. When all of the companion’s outer layers were gone, all that was left was its dead core: a white dwarf — a super-dense ball that’s a third as massive as the Sun but only about the size of Earth.

Regulus has two more companions, but they’re a long way from the bright star — about 4,000 times farther than Earth is from the Sun. They form a widely separated pair. One of the stars is a bit smaller and cooler than the Sun, while the other is a red dwarf — a bare cosmic ember. From the system’s distance of almost 80 light-years, you need a telescope to see even the combined light of these two stars — faint companions to the lion’s mighty heart.


Script by Damond Benningfield, Copyright 2013

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