Eighteenth-century astronomer William Herschel described the star system 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 southwestern sky in early evening. It’s wedged between brilliant Orion and the “little dog” star Procyon.

There’s not much to see in Monoceros with the eye alone. But telescopes reveal a bounty of beautiful sights. And 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 the same beauty that Herschel did, you need a telescope. That view reveals three stars, not one, all with a fetching blue-white color.

The color comes from the temperatures of the stars – their surfaces are many thousands of degrees hotter than the Sun’s. And all three stars are much more massive than the Sun. That revs up the nuclear reactions in their cores, which is what makes them so hot. It also makes the stars extremely bright – as much as 3200 times as bright as the Sun. So the stars are visible across 700 light-years of space.

The two faintest members of the system probably form a wide binary, with the third star orbiting around them. Combined, they make Beta Monocerotis a beautiful skywatching sight – a vision in blue for an early-spring night.

Script by Damond Benningfield