The Christmas Tree Cluster is an open cluster of stars in NGC 2264 about 2,500 light years away from Earth in the constellation Unicorn. It owes its name to the fact that it resembles a Christmas tree in visible light. It is a very young and very interesting star formation region by astronomical standards.

The dense gas nebula does not allow the light of the protostars to get out, so that we cannot see them. The Spitzer infrared telescope delivers very impressive images that are extremely informative for astronomers. Here you can experience the formation of stars almost live. The arrangement of the young stars seems to confirm the theory that their distance depends on the density and temperature of the gas cloud.

The Cone Nebula is a dark cloud in conjunction with an H-II region, also embedded in NGC 2264, making the Cone Nebula a part of the nebula surrounding the Christmas tree cluster. The diffuse cone-like nebula is located in the southern part of NGC 2264 and takes the form of a dark absorption nebula consisting of cold molecular hydrogen and dust in front of a weak emission nebula ionized by S Monocerotis, the brightest star in NGC 2264. The faint nebula is about seven light years long.