Unusual Globular Cluster Messier 71
This Hubble Space Telescope image shows a bright scattering of stars in the small constellation of Sagitta (the Arrow). This is the center of the globular cluster Messier 71, a great ball of ancient stars on the edge of our galaxy around 13,000 light-years from Earth. M71 is around 27 light-years across.
Globular clusters are typically seen in the galactic suburbs, large bright balls of stars found above and below the main body of the galaxy. These clusters are tightly bound together by their gravitational attraction, hence their spherical shape and their name. ("Globulus" means “little sphere” in Latin.) Around 150 such globular clusters are known to exist around our Milky Way, each one of them containing several hundred thousand stars.
Despite being a familiar object, Messier 71’s precise nature was disputed until recently. Since it is not nearly as dense as other globulars, some thought it to be a large "open" star cluster. This was the dominant view for many years. But in the 1970s, astronomers concluded that it is in fact a relatively sparse globular cluster. The stars in Messier 71, as is usual in such clusters, are quite old, at around 9 to 10 billion years, and consequently are low in elements other than hydrogen and helium.
For more information, visit: www.spacetelescope.org/images/potw1018a/
Credit: ESA/Hubble and NASA
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Unusual Globular Cluster Messier 71
This Hubble Space Telescope image shows a bright scattering of stars in the small constellation of Sagitta (the Arrow). This is the center of the globular cluster Messier 71, a great ball of ancient stars on the edge of our galaxy around 13,000 light-years from Earth. M71 is around 27 light-years across.
Globular clusters are typically seen in the galactic suburbs, large bright balls of stars found above and below the main body of the galaxy. These clusters are tightly bound together by their gravitational attraction, hence their spherical shape and their name. ("Globulus" means “little sphere” in Latin.) Around 150 such globular clusters are known to exist around our Milky Way, each one of them containing several hundred thousand stars.
Despite being a familiar object, Messier 71’s precise nature was disputed until recently. Since it is not nearly as dense as other globulars, some thought it to be a large "open" star cluster. This was the dominant view for many years. But in the 1970s, astronomers concluded that it is in fact a relatively sparse globular cluster. The stars in Messier 71, as is usual in such clusters, are quite old, at around 9 to 10 billion years, and consequently are low in elements other than hydrogen and helium.
For more information, visit: www.spacetelescope.org/images/potw1018a/
Credit: ESA/Hubble and NASA
Find us on Twitter, Instagram, Facebook and YouTube