|Designation||Part of NGC 2264|
|Right ascension||06h 41m 15s|
|Type of object||Diffuse nebula|
|Magnitude||Apparent Mag: +3.9|
|Distance from Earth||2,700 ly|
|Radial velocity||17.68±2.26 km/s|
|Proper motion|| RA: -0.63 mas/yr|
Dec.: -3.88 mas/yr
The Cone nebula is a diffuse nebula in the constellation of Monoceros, the Unicorn. Its name derives from its cone-like shape. It is part of the Christmas Tree Cluster of stars and shares the same designation of NGC 2264 in the New General Catalogue.The shape of the nebula bears close resemblance to the famous Pillars of Creation. The nebula was first observed by William Herschel on December 26, 1785 and catalogued it as H V.27. Herschel had already discovered the Christmas Tree cluster two years prior.
Properties and Structure
The nebula consists of a dark nebula that obscures the light from an emission nebula behind it. Composed of gas and interstellar dust, the emission nebula is illuminated by the star 15 Monocerotis, a large variable star. This gives the nebula an unusual property of having a variable brightness. The ultraviolet radiation produced by this star and others in the Christmas Tree Cluster is responsible for the reddish glow of the nebula. This radiation excites hydrogen in the nebula, which then dexcites emitting a characteristic red color. Infrared analysis of the nebula has shown at least seven stars buried deep within the nebula and are not visible with optical telescopes. The radiation from these stars provides an outward pressure that is likely to be responsible for the shape of the nebula. The pillar has an apparent length of some 10 arcminutes, which means it is around 7 light years long.