Famed 18th-century astronomer William Herschel described the star system known today as Beta Monocerotis as “one of the most beautiful sights in the heavens.” It’s one of the hidden beauties of Monoceros, the unicorn. The constellation is well up in the southeastern sky in early evening, between the little dog star Procyon, and Betelgeuse, the orange shoulder of Orion.
There’s not much to see in Monoceros with the eye alone. But telescopes reveal a bounty of beautiful sights. Beta Monocerotis straddles both domains. It’s faintly visible to the unaided eye as one of the unicorn’s two brightest stars. But to see it as Herschel did, you need a telescope. That view reveals three stars, not one, all with a lovely blue-white color.
The color comes from their surface temperature — all three are many thousands of degrees hotter than the Sun. They’re also more massive than the Sun. That great heft revs up the nuclear engines in their cores, which is what makes their surfaces so hot. It also makes the stars extremely bright — up to about 3,000 times as bright as the Sun — bright enough to see from a distance of 700 light-years.
The two faintest members of the system probably form a wide binary, with the brightest of the three stars in orbit around them. Combined, they make Beta Monocerotis a beautiful skywatching sight for a chilly winter night.
We’ll talk about one of the other treasures of Monoceros — a busy stellar nursery — tomorrow.
Script by Damond Benningfield, Copyright 2014
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