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Wildrik Botjes Planetarium
Physics & Astronomy Department

Astr112 Photography Projects, Fall 2007

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Open Star Cluster (NGC 6871) Matthew Hall

Open star cluster NGC-6871

NGC 6871 is an open star cluster which can be seen in the constellation Cygnus. Little has been written about NGC 6871 since it was first catalogued in 1888 by Dreyer. Open star clusters are groupings of up to a few thousand stars that developed from the same molecular cloud. Because they formed at the same time in the same region, stars in a cluster tend to have similar chemical compositions. Unlike globular clusters, open clusters are only loosely bound to each other by gravity, and will drift apart from each other over the course of time. It is not known how distant NGC 6871 is. If we were to estimate that it were 1000LY away, then the portion of the cluster seen above would be approximately 4x6LY.

The large, blue-white stars near the middle of the image are the heart of the cluster, and several of the other similar stars are also part of cluster NGC 6871. The cluster extends beyond the edges of this image. The light blue color of the stars in the cluster indicates that these stars are of type B, with an approximate surface temperature of 10,000-30,000 degrees Kelvin. Many other stars can be seen in the background. The full range of stellar types can be observed, from the red and orange Ks and Ms to the bright blue Os.

References:

"NGC6871" Students for the Development and Exploration of Space <http://seds.org/~spider/ngc/ngc.cgi?n6871>

Right Ascension (J2000) 20:05:54
Declination (J2000) 35:47:00
Filters used blue(B), green(V) and red(R)
Exposure time per filter

20x2 seconds in RV,

20x4 seconds in B

Date observed

November 11, 2007