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Astronomical Observatory: Cool Images


Astr110 Photography Projects, Fall 2005

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M2 Star Cluster, Andrea Bailey

M2 Star cluster

This is the globular star cluster M2, found in the Aquarius constellation. Like most globular star clusters, it lies outside the plane of the galaxy, in the halo. Most globular star clusters contain more than a million stars, with many packed into a dense core. The core of the M2 star cluster is 3.7 light years in diameter, only a fraction of its total diameter. Over 10,000 stars are packed into that area. The overall spectral type of this cluster is F0. Globular clusters rely on gravity in order to hold them together, and as a result, there are stars constantly moving from the interior of the cluster, and back out again. As two stars come close to each other, they interact and can be sent speeding off in an entirely new direction. An observer could never pinpoint any specific star in a cluster, because they are in constant motion, propelled by gravity.

This image was taken as a black and white deep photograph, in order to enhance the brightness of the cluster. We can see its densely packed core in the center of the cluster. However, the actual measurement of the entire cluster spans much farther, nearly to the edges of the photograph. Its actual linear size is 290 lightyears. What we cannot see in this photo, however, are the colors of the stars. This particular star cluster has many red and yellow giants, letting the observer know that it is an older star cluster, with many dying stars. Objects such as this one are very useful in the study of the effects that stars gravity have on one another, and studying the age of a cluster.


"Messier Object Index", Messier Object M2

"Aquarius Constellation"

The Cosmic Perspective, 3rd Edition, Bennett, Donahue, Scheider, Voit

Right Ascension (J2000) 21:33:30
Declination (J2000) -00:49:00
Filters used clear(C)
Exposure time per filter 4 x 60 seconds
Date observed

November 15, 2005 (C)




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