NGC 2264 is a star-forming region located about 2,500 light years away in the constellation of Monoceros (the Unicorn). Within this beautiful region are both the Snowflake Cluster and the Cone Nebula.
The Snowflake Cluster
Observations with the Spitzer Space Telescope (below) show the Snowflake Cluster (boxed in green) in exquisite detail. This image is a five-channel composite showing emission at 3.6 and 4.5 microns (blue), 5.8 microns (cyan), 8 microns (green), and 24 microns (red). The stars in this cluster lie along linear structures that resemble the spokes of a wheel or the pattern of a snowflake, garnering the cluster the name ‘Snowflake Cluster.’ These stars are clearly young (only ~100,000 years old), because they have yet to drift from their initial birth location. Over time we can expect this pattern to break apart as the drifting motions of the stars move them away from this initial clump.
A recent paper by Teixeira et al. (2012) examines the disk population of NGC 2264. They conclude that the region must have undergone multiple star-forming events. The population of stars with anaemic inner disks appears more evolved and is more dispersed. These stars must have formed before others in the region with thick embedded disks. Below, is a map of the spatial distribution of sources in the NGC 2264 region. The left panel shows sources with thick disks, of which many are embedded (filled circles). A significant number of these sources are clustered along the spokes of the Snowflake Cluster. The right panel shows sources with anaemic disks, of which none are embedded. These sources trace a more extended population.
The Cone Nebula
Further to the south (below the Snowflake Cluster) is the Cone Nebula, a dramatic edifice of gas and dust. This pillar is 7 lightyears in length. That’s nearly twice the distance from the Earth to the nearest star! In the Hubble Space Telescope image shown below, we are looking at just the top 2.5 lightyears of the nebula. Over time, radiation from hot, young stars formed in the surrounding region is slowly eroding away the nebula. These young stars produce ultraviolet radiation that heats the edge of the cloud. This high energy (short wavelength) emission releases gas into the surrounding space. Further heating causes this hydrogen gas to glow red (H-alpha emission), producing the red halo seen in the image. Eventually, only the densest regions of the Cone Nebula will be left. Over time, stars and planets may form out of these dense regions.