Cone Nebula

NGC 2264 is a single catalogue entry covering two objects that are usually photographed together: the Christmas Tree Cluster, a loose group of hot young stars in Monoceros, and the Cone Nebula, the dark pillar of dust at its southern edge. Both sit around 2,600 light-years away in the Mon OB1 association, one of the nearest regions of ongoing massive star formation. The cone itself is a column of cold molecular gas roughly seven light-years long, and its shape is not accidental — it is the shadow of denser material resisting the ultraviolet flood from S Monocerotis, the brilliant O7 star at the top of the field. Radiation erodes the cloud from every side except the one the pillar shields, so the tip always points away from the star doing the damage. The same process is compressing the gas inside, and infrared surveys have found protostars and Herbig-Haro jets buried throughout the region, still assembling. The blue haze west of the cluster is the Fox Fur Nebula, starlight scattering off dust rather than gas glowing under its own power.