Globular Clusters

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A globular star cluster is a nearly spherical collection of hundreds of thousands of densly packed stars that are tightly bound together by gravity. Most of the stars in a given cluster were born at the same time, from the same giant molecular cloud, and share a common chemical composition and age. The primary difference between individual stars within the cluster is therefore their mass. These clusters are perhaps the oldest stars in the galaxy, and form an important "laboratory" for the study of stellar evolution. Most globular clusters consist of metal-poor stars (in astronomy, a "metal" is any element heavier than hydrogen and helium), consisting mostly of ancient stars that are 10-12 billion years old. Globular clusters tend to be found in the outer halo of a galaxy, taking a roughly spherical distribution in the Milky Way, where there are approximately 150 known globular clusters.


M13 (NGC 6205) in the constellation Hercules

M3 (NGC 5272) in the constellation Canes Venatici

distance: 25,100 light-yearsdistance: 33,900 light-years
estimated age: ~12 billion yearsestimated age: ~11.75-12.5 billion years
apparent diameter: 23 arc-minutesapparent diameter: 18 arc-minutes
total mass: 5.5 x 105 solar massestotal mass: 4.1 x 105 solar masses
8-inch f/8 RC telescope8-inch f/8 RC telescope
QHY268M monochrome camera / Astronomik LRGB filtersQHY268M monochrome camera / Astronomik RGB filters
exposure: 3x16x180sec RGB / 32x180sec Luminanceexposure: 3x16x180sec RGB
Processing: Pixinsight-->Photoshop-->Topaz deNoise AI-->LightroomProcessing: Pixinsight-->Photoshop-->Topaz deNoise AI-->Lightroom



M92 (NGC 6341) in the constellation Hercules


distance: ~27,000 light-yearsdistance: xx
estimated age: ~11-13.5 billion yearsestimated age: xx
apparent diameter: 14 arc-minutesapparent diameter: xx
total mass: 3.52 x 105 solar massestotal mass: xx
8-inch f/8 RC telescopexx
QHY268M monochrome camera / Astronomik LRGB filtersxx
exposure: 3x14x180sec RGB / 11x300sec Luminancexxx
Processing: Pixinsight-->Photoshop-->Lightroomxx


1. Martinez, Perez and Sanchez, ed. "Globular Clusters," Cambridge University Press, 1999

2. Milky Way Globular Clusters (

3. VandenBerg, Brogaard and Leaman, "The Ages of 55 Globular Clusters as Determined using an Improved dV Method along with Color-Magnitude Diagram Constraints, and their Implications for Broader Issues." Astrophysical Journal, 2013, 775, 134V