Located on the celestial equator, Monoceros is faint constellation, whose name means unicorn in Greek. Petrus Plancius is attributed with the creation of the constellation in the 17th-century.

One of the nearest known black holes to our Solar System is in this constellation, which is located roughly 3,300 light-years away. The black hole is estimated to be 6.6 solar masses.

Monoceros contains two super-Earth exoplanets in one planetary system. In the constellation, there are a few fourth magnitude stars, and is home to several notable stars including variable stars S Monocerotis, R Monocerotis, and V838 Monocerotis, and Plaskett’s Star.

	Applicable Information
Visibility In Pacific Northwest	October to March
Best Times To View	February
Right Ascension	7.15h
Declination	−5.74°
Area	482 square degrees
Main Stars	4
Brightest Object	β Mon
Meteor showers	December Monocerids, Alpha Monocerids
Messier objects	1
Neighboring Constellations	Canis Major, Canis Minor, Gemini, Hydra, Lepus, Orion, Puppis

History

In Western astronomy, Monoceros is a relatively modern constellation, as it is not one of Ptolemy’s 48 in the Almagest. The constellation first appeared on a globe created by the Dutch cartographer Petrus Plancius around 1612, but was later charted by German astronomer Jakob Bartsch in 1624.

Chinese asterisms Sze Fūh, the Four Great Canals; Kwan Kew; and Wae Choo, the Outer Kitchen, all lay within the boundaries of Monoceros.

Stars

Monoceros contains only a few fourth magnitude stars, making the constellation difficult to see with the naked eye. Alpha Monocerotis has a visual magnitude of 3.93, while Gamma Monocerotis has a visual magnitude of 3.98.

Monoceros contains many clusters and nebulae. The 1 Messier object in the constellation is Messier 50, which is an open cluster. The Rosette Nebula, which is made up of NGC 2237, 2238, 2239, and 2246, is a diffuse nebula with a magnitude of 6.0.

The open cluster NGC 2264, otherwise known as The Christmas Tree Cluster, gets its name for its resemblance to a Christmas Tree. The cluster is bright with a magnitude of 3.9, as the variable star S Monocerotis represents the tree’s trunk. The variable star V429 Monocerotis represents the top of the cluster.

The very dim nebula NGC 2264 is called the Cone Nebula contains a dark conic structure, is very visible in photographs but hard to view in telescopes.

The nebula NGC 2261, called Hubble’s Variable Nebula, as named for Edwin Hubble. The star’s unique interaction with the material in the nebula makes it both an emission nebula and a reflection nebula has been of much interest to scientists.

Make sure to check out other articles on the site, including a brief introduction to constellations, other constellation articles, and more!