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Moon and Regulus

January 25, 2016

The Moon keeps company with a “royal” star tonight. Regulus, the brightest star of Leo, the lion, is quite close to the left of the Moon as they climb into good view around 8 or 9 o’clock.

The name “Regulus” means “the little king.” It comes from an ancient idea that the star was one of the rulers of heaven.

The star that we see as Regulus is quite impressive. It’s bigger and heavier than the Sun, and several hundred times brighter. And like any monarch, it has an entourage — at least three companion stars.

One of them is a white dwarf — a stellar corpse that orbits quite close to Regulus. The star was once the more impressive of the two. As it neared the end of its life, though, it expelled its outer layers of gas. Some of the gas fell onto Regulus, making it bigger and brighter, and causing it to spin much faster.

The other companions are much farther away from Regulus — about a hundred times the distance from Earth to Pluto. Through a small telescope, their light blurs together to form a single pinpoint.

The two stars are known as Regulus B and C, and they form their own binary — they orbit each other, and the pair orbits Regulus and its close companion. One of the stars is a little smaller and fainter than the Sun, and glows yellow-orange. The other is smaller still — a faint ember known as a red dwarf. It’s only about a third as massive as the Sun, and less than one percent as bright — a feeble attendant for a “regal” star.

Script by Damond Benningfield, Copyright 2015

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