Beta Monocerotis is one of the most beautiful triple star systems in the heavens — three blue-white points of light that make a skinny triangle. But the system is even more remarkable than it looks. All three of its stars are among the brightest and the most massive in the galaxy.
Two of the stars are roughly six times as massive as the Sun, and more than a thousand times brighter.
The third star probably orbits the other two. But it’s so far that it takes about nine days for its light to cross the vast gulf between them. So astronomers aren’t yet certain that it’s actually tied to them. Either way, it’s the most impressive of the triplets. It’s heavier than the others, and about twice as bright.
Like the Sun, all three stars will end their lives as cosmic embers known as white dwarfs. But they’ll get there a lot faster than the Sun. Heavier stars use up their nuclear fuel more quickly, so they live shorter lives. The stars of Beta Monocerotis will live less than one percent as long as the Sun before they enter the final phases of life. For a short while, before they become white dwarfs, each of them will shine much brighter than it is today.
For now, look for Beta Monocerotis in the southeast at nightfall. Although it’s the brightest star of Monoceros, the unicorn, it’s quite faint, so you need dark skies to see it. But it’s to the lower left of Orion’s Belt, so there’s a prominent marker to point the way.
Script by Damond Benningfield