NGC 1851 (Caldwell 73) is a dense, massive globular star cluster in the constellation Columba, about 40,000 light-years away, known for its unusual features like multiple stellar populations of different ages and a surrounding stellar halo, suggesting it may be the remnant core of a dwarf galaxy that merged with the Milky Way. It's visible with binoculars as a fuzzy patch and can be resolved into individual stars with a small telescope, appearing as a bright, condensed ball of light.
Type: Globular cluster
Location: Constellation Columba, about 39,500 light-years from Earth
Apparent Magnitude: 7.3
Age: Estimated 9.2 billion years old
Mass: 551,000 times the mass of the Sun
Multiple Stellar Populations: Contains stars of different ages, unlike most globular clusters.
Stellar Halo: Surrounded by a diffuse halo of stars that extends far beyond the main cluster.
Formation Theory: The multiple populations and halo suggest it might be the stripped nucleus of a dwarf galaxy that was consumed by the Milky Way.
Binoculars: Appears as a fuzzy patch of light.
Small Telescopes: Can resolve some individual stars, especially away from the bright center.
Larger Telescopes: A 12-inch scope can resolve it into a large, bright, round ball of stars. Image Credit NASA Hubble Space Telescope
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