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Moon and Regulus

December 17, 2016

Many of the stars that sparkle across a dark sky are deceptive — there’s much more to them than the eye can see. That’s because most of those points of light are the combined glow of two or more stars.

A famous example is Regulus, the bright heart of Leo, the lion. It stands close to the lower left of the Moon as they climb into good view by around 11 o’clock tonight.

What we see as Regulus is a star that’s bigger and hotter than the Sun, and hundreds of times brighter. But the star has at least three companions. They’re all so faint, though, they they add little or nothing to the light we see from the system’s main star.

One of the companions is a white dwarf — the dead core of a star that was once more impressive than the visible star. It’s so close to the main star that it’s impossible to see through the glare.

The two other known stars also form a pair. They’re hundreds of billions of miles away from the bright pair, so they are visible through a telescope.

The brighter member of this pair is a bit smaller, cooler, and fainter than the Sun. And its companion is cooler and fainter still — a bare cosmic ember that’s only a small fraction of the Sun’s brightness. The two stars are separated by about a hundred times the distance between Earth and the Sun, so it takes them centuries to complete a single orbit around each other — illuminated by the brilliant glow of the star we know as Regulus.

Tomorrow: twisted spirals.


Script by Damond Benningfield


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