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Christmas Tree Cluster (NGC 2264)
Stephanie Slotsema

NGC 2254

This is an artificially colored image of the Christmas Tree Cluster, known to astronomers as NCG 2264. The cluster was first discovered by William Herschel on January 18, 1784. The Christmas Tree Cluster is located in the greater Monoceros constellation, along with the Cone Nebula, Fox Fur Nebula, and Snowflake Cluster. As an "open cluster", it is a group of up to a few thousand stars that formed from the same giant molecular cloud, loosely bound to each other via gravitational attraction. This cluster has been disrupted, likely by close encounters with other clusters and clouds of gas, a trait common to open clusters. The area's current status is that of an active star forming region.

This image contains the brightest star in the Monoceros constellation, which serves as the "tree trunk" of the Christmas tree shape in the wider sky. It lies 2.4 thousand light years from earth (Frommert & Kronberg). I estimated an angular distance of 20.0 arc minutes, and using the small angle formula, I calculated its linear size to be 1.32 x 10^14 km, or about 14 light years. The natural coloring of the image shows large blue stars pushing through red-colored surroundings. These large stars (including the central star in this image and the trio below) illuminate areas around them as young, hot stars. This image also shows higher concentrations of stars to the left of the cluster. The dark, empty space to the right of the cluster is due to dust regions on the near side of the image blocking illumination of background stars. A similar dark texturing is seen in "finger smudges" to the right of the central star.

Because the image I wished to study was bigger than the normal field of view, I chose to matrix four images of 15.8 arc minutes by 10.4 arc minutes. The resulting image you see above is about 30 arc minutes wide and 20 arc minutes high. Clicking on the image will enlarge it on your screen. The entirety of the Christmas Tree Cluster extends even farther below this image. The matrixed images were taken in black and white color, but I artificially colored the resulting image red. I chose this color because of the vast amount of hydrogen gas in the image. The red color highlights this.


Frommert, Hartmut, and Christine Kronberg. "NGC 2264 ." Students for the Exploration and Development of Space. Accessed 12 Apr. 2011. <>.

Frommert, Hartmut, and Christine Kronberg. "Open Star Clusters." Students for the Exploration and Development of Space. Accessed 12 Apr. 2011. <>.

"SIMBAD Astronomical Database." Centre de Donnes Astronomiques de Strassbourg. Accessed 12 Apr. 2011. <>

Right Ascension (J2000) 06:41:05
Declination (J2000) +09:53:00
Filters used R (Red)
Exposure time per filter R (60s x 5) for four mosaic fields
Date observed March 24, 2011 EDT



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