M13, also called the Hercules Globular Cluster, has more than 100,000 stars that shine from about 25,000 light-years away.
Credit: Bob and Janice Fera
The hundreds of thousands of stars that make the mighty Hercules globular cluster shine bright in this skywatching photo.
Astrophotography team Bob and Janice Fera took this image in May 18 and 20, 2012 from Eagle Ridge Observatory in Foresthill, Calif.
Also known as M13, this cluster has more than 100,000 stars that shine from about 25,000 light-years away. The brightest stars are packed tightly at the core and sometimes slam into each other creating new stars called “blue stragglers.”
These blue stars shine a bluish-white because their core temperatures are extremely hot. Bright red stars found within the cluster are cooler because they are older stars that have expanded in size. These stars are often called ancient red giants.
The Feras used an Officina Stellare RC-360AST 14" f/8 Ritchey Chretien Cassegrain telescope with two-element field flattener to observe the M13 cluster. An Apogee Alta U16M CCD camera with Astrodon filters was used to capture the image.
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