Skip to Navigation | Skip to Content

Previous image Up to Astr111 Index Next image ASTR 110 Photography Projects, Fall 2015

M15 Star Cluster (NGC 7078) & M52 Star Cluster (NGC 7654)
Albert Awuah & Tyler Sajdak

M15 M52
M15 Star Cluster - Albert Awuah M52 Star Cluster- Tyler Sajdak

The objects above represent two different varieties of star clusters. Star clusters are groups of stars which are held together by gravity. There are two main types of star clusters that have been discovered: globular clusters, which are compact groups of hundreds of thousands of very old stars, and open clusters, which usually contain less than a few hundred stars, and are often very young.

The first object, M15, is a globular cluster. In terms of density, M15 is probably the most dense of all globular star clusters in our Milky Way galaxy. Moreover, globular cluster M15 contains 9 known pulsars, which is a considerable number. Pulsars are highly magnetized, rotating neutron stars which are, in this case, all that remains from the ancient supernova explosions that took place in the time when M15 was young. M15 was also the first globular cluster in which a planetary nebula (Pease 1 or K 648) could be identified.

The second object, M52, is an open cluster. Open clusters are found in the disks of galaxies. Most open clusters of stars generally contain a few hundred stars with a diameter across the cluster of about 10 light-years. Since they are far less dense and populated than globular clusters, they are not held together as tightly by gravity. Open clusters therefore tend to break up over time as they encounter other cosmological objects and forces.

Both clusters are collections of stars held together by a mutual, give-and-take gravitational attraction. All the stars in each of the two types of clusters are the same age as they were formed from the same cloud of gas and dust. In both cases, each cluster orbits the center of a galaxy.

Globular clusters are groups of thousands to hundreds of thousands of stars whereas open clusters are generally smaller and contain hundreds of stars. Globular clusters are located in the halo or bulge of a galaxy whereas open clusters are located in the arms of spiral galaxies. Globular clusters are no longer forming in our galaxy, the Milky Way, whereas open clusters continue to form in the arms of the Milky Way galaxy.


"Messier Object 15." SEDS Messier Database. N.p., n.d. Web. 24 Nov. 2015. <>.

Frommert, Hartmut, and Christine Kronberg. "Messier 52." Messier Object 52. N.p., 24 Apr. 2013. Web. 24 Nov. 2015

"Amazing Space- Graphic Organizer: Star clusters compared." Space Telescope Science Institute. STSI, n.d. Web. 2 Dec. 2015. <>.

Kaler, James B. "Clusters." Clusters. University of Illinois, n.d. Web. 2 Dec. 2015. <>.


Object M15 M52
Right Ascension (J2000) 21:29:58 23:24:50
Declination (J2000) 12:10:01 +61:34:56
Filters used B (Blue), C (Clear), R (Red), V (Green) B (Blue), C (Clear), R (Red), V (Green)
Exposure time per filter B: 300, V: 180, and R: 240; C: 240 B: 300, V: 180, and R: 240; C: 240
Image dimension 904x617 pixels; 19.58x13.37 arcminutes 701x481 pixels; 15.18x10.42 arcminutes
Date/time observed October 25, 2015, 05:12 UT October 1, 2015, 11:46:59' UT



Secondary content.


Side content.