You are looking at a picture of NGC 6997, an open star cluster contained within the North American Nebula (NGC 7000). Open star clusters are formed when giant molecular clouds collapse, initiating bursts of star formation that often result in clusters. Star clusters are considered to be the building blocks of galaxies. They are loosely bound together by gravitational attraction, but many stars carry the escape speed necessary to break free of the cluster, eventually becoming indiscernible from the surrounding stars in the night sky. Open clusters exhibit far less attraction than their globular cluster cousins, and are thus expected to survive only a few million years.
NGC 6997 is a very recent open cluster to develop, and is likely the product of the surrounding cloud of hydrogen gas that comprises the North American Nebula. The eerie red background seen in the image is precisely this hydrogen gas. If examined closely, it is also easy to see the contours of the nebula itself. This is because NGC 6997 is located on the "East Coast" of the nebula. The cluster of stars seen in the image are thus to the west of the nebula. The bright blue stars seen within the nebula are the most massive members found within the cluster. Because they have both large size and high temperature, they burn very bright and very blue. The first documented finding of NGC 6997 was in 1786, by William Herschel. The distance to this object is estimated to be X; we find a maximum angular size of Y arcminutes, which corresponds to a linear size of Z.
"Open cluster." Wikipedia. <http://en.wikipedia.org/wiki/Open_cluster>.
"NGC 7000." Students for the Exploration and Development of Space. <http://messier.seds.org/xtra/ngc/n7000.html>.
|Right Ascension (J2000)||20:56:39|
|Filters used||B (Blue), R (Red), V (Green)|
|Exposure time per filter||B, V, and R (6s)|
|Date observed||October 25, 2012|