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Astronomical Observatory: Cool Images

Astr111 Photography Projects, Spring 2007

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M4 Globular Cluster (NGC 6121), Carly Williams

M95 Spiral Galaxy

Messier 4 is a globular cluster located about 7,200 light-years away, making it one of the nearest globular clusters in the sky. It was discovered by Philippe Loys de Chéseaux in 1746. A globular cluster contains ten thousand to one million stars spread out over a volume of up to 200 light years in diameter. Numerous stars that are around the same age, distance, and chemical composition make up open star clusters. M4 can easily be spotted by the naked eye; it is a few degrees west of the bright Antares and just south of the line to Sigma Scorpii. The cluster contains white dwarf stars, which are some of the oldest stars in our Milky Way Galaxy.

As you can tell from the image above, M4 is one of the brightest globular clusters in the sky. The above image is composed of four separate photographs mosaic into one image because of the immense size. Often the globular cluster can be obscured by dark clouds of interstellar matter causing the color of the light from the cluster to redden. Its angular diameter is about thirty six minutes of arc while the linear diameter is about 75 light years. It is easy to see that the cluster of stars extends gradually with many bright stars standing out in the middle.

Frommert, Hartmut and Kronberg, Christine. "Messier 4." Messier Object 4. 18 001 2005. 3 Apr 2007.

Frommert, Hartmut and Kronberg, Christine. "Globular Star Clusters." Globular Star Clusters. 15 005 2005. 3 Apr 2007.

Verschatse, Daniel. "Messier 4." Antilhue - Chile. 28 011 2006. 3 Apr 2007.

Right Ascension (J2000) 16:23:35.41
Declination (J2000) -26° 31′ 31.9″
Filters used Clear
Exposure time per filter 5x60 seconds in each of the four fields
Date observed

March 18, 2007




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