Messier 5 (M5) is an ancient, massive globular star cluster in the constellation Serpens, containing over 100,000 stars and estimated to be nearly 13 billion years old, making it one of the oldest in the Milky Way. Discovered in 1702, it appears as a faint, fuzzy patch in binoculars but resolves into thousands of individual stars in larger telescopes, revealing a bright core and a halo of aging stars, including many variable stars (RR Lyrae) that are useful for measuring cosmic distances.
Type: Globular star cluster
Location: Constellation Serpens, about 25,000 light-years away
Age: Approximately 13 billion years old
Size: About 165 light-years in diameter
Stars: 100,000 to 500,000 stars, including over 100 variable stars (RR Lyrae type)
Naked eye: Visible as a faint, fuzzy point under very dark skies.
Binoculars: Appears as a small, fuzzy patch.
Small telescope: Shows a bright core with a fainter halo.
Larger telescope: Resolves thousands of individual stars, appearing elongated with a dense center.
Ancient population: Its age makes it a key object for studying stellar evolution.
Variable stars: The high number of RR Lyrae variables makes it important for distance measurement.
"Blue stragglers": Contains some younger-looking stars that are thought to have formed from the merger of two older stars. Image Credit NASA, ESA, G. Piotto
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