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Physics & Astronomy Department

Astr110 Photography Projects, Fall 2005

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Hole-In-A-Cluster, Amy Jeltema and Stephanie Kooyman

Hole-in-a-Cluster

Above is a picture taken of the an open star cluster called Hole-In-A-Cluster. An open star cluster is a grouping of stars that contains a few hundred to a few thousand stars. It usually is about 30 lightyears in size. There is not enough mass for gravity to hold the cluster together. All stars in the cluster form out of the same could of gas and dust and they all form at the same time. There are over 1100 open clusters that are known in our Milky Way Galaxy.

The Hole-In-A-Cluster is a medium sized open cluster in Cygnus that was given this name because there is a notable lack of stars in the central region of the cluster. If you look at the picture above you can see that there are areas with almost no stars at all. The area with no stars at all could be due to the fact that gravity is pulling on the cluster and therefore the stars could be starting to disperse. Another option could be that dust is covering some of the stars in the center of the cluster.

The Hole-In-A-Cluster is made up of many different color stars. The colors range from blue to red. This tells us the each star varies in surface temperature. The stars that are more blue have a hotter surface temperature and the stars that are more red have a cooler surface temperature. The different colors of the stars also are able to tell us about the age that they are. The blue stars are younger and the red stars are older. The angular size of our object is 13' and the linear size is 14.9 Lightyears. This would take one a very, very long time to get there.

References:

NGC 6811

WEBDA: Page for Open Cluster NGC6811
Bennett, Jeffrey. The Cosmic Perspective. 3rd ed. Pearson Education, 2004.

Right Ascension (2000) 19:37:29
Declination (2000) 46:24:55
Filters used blue(B), green(V), red(R)
Exposure time per filter 10 seconds(VR), 60 seconds(B)
Date observed

November 3, 2005 (B)
November 5, 2005 (RV)