Monoceros is situated on the celestial equator, bordered by Orion, Canis Major, and Canis Minor. The center of this constellation straddles the Milky Way, where many nebulae and star clusters are found. It is best seen in the northern hemisphere between December and May.
History and Mythology
Monoceros is a relatively modern constellation, first appearing on the star maps of the German astronomer Jakob Bartsch in 1624. Bartsch used some of the fainter stars from the surrounding constellations to make up the body of the Unicorn.
Monoceros was also found on a Persian globe around 1600. It depicts the Unicorn as having the body of a horse with a single horn in the middle of its forehead. Pictures of this animal were found in wall paintings by the Assyrians dating back to 2,700 BC.
Some people believe that the unicorn might actually be a misinterpretation of the rhinoceros. Many of the superstitions regarding the powers of the horn of the Unicorn are the same as those of the rhinoceros' horn.
Notable Objects
Alpha Monocerotis is a 4th magnitude star 175 light-years away. Beta Monocerotis is a remarkable triple star system with components of magnitudes 4.5, 5.2, and 5.6. They form an arc of blue-white stars. It is 690 light-years away.
The winter portion of the Milky Way runs diagonally through Monoceros. There are several bright clusters in Monoceros. M 50 is a 6th magnitude open cluster consisting of about 80 stars. It is located on the southern edge of the constellation, near the border with Canis Major. NGC 2301 is also a 6th magnitude open cluster, comprised of 80 stars from 8th magnitude and fainter.
The Cone Nebula, NGC 2264, is a cloud of dark material in which new stars are being born. The associated star cluster is sometimes referred to as the "Christmas Tree" cluster.
Hubble's Variable Nebula, NGC 2261, lies just south of the Cone nebula, and is visible with large amateur telescopes. NGC 2261 is a triangular cloud of dust lit by the variable star R Monocerotis. At its brightest, this star is magnitude 9.5. It fluctuates down to about 12th magnitude; as it does so, the brightness and shape of the nebula also varies. This was discovered by the American astronomer Edwin Hubble; Hubble's Variable Nebula was the first object to be photographed with the 200 inch Hale Telescope when it opened on Mount Palomar in 1948.
The Rosette Nebula is a shell of gas that surrounds the open cluster NGC 2244. The stars in this cluster are thought to be very young - perhaps no more than one half million years old. It is best seen in a wide field telescope at low power. It appear as a diffuse cloud with the star cluster NGC 2244 at the center.