Beta Monocerotis (β Mon) is a triple star system in the constellation of Monoceros. All three stars (β Mon A, β Mon B, and β Mon C) in the system are hot, blue-white class B3 main-sequence stars. All of them are brighter and more massive than the Sun, their masses being 6 to 9 times solar mass and luminosities around 1300 to 3200 times the luminosity of the Sun. Stars B and C orbit each other and A orbits them.

In the night sky, the constellation of Monoceros is near the constellation of Orion. β Mon is located between Orion's Belt and Sirius.

You can see β Mon by naked eye, even in urban environment, but it just looks like a dim star. To see it, continue a line defined by Orion's Belt until it forms an angle of 135º with a line defined by α CMa (Sirius) and δ CMa. Around there twinkles β Mon. But to see that it actually is a triple star system you'll need some equipment.