It took more than 200 years to find out, but a globular cluster discovered in 1778 by comet-hunter Charles Messier turned out to be the first such star swarm located outside the Milky Way. As astronomers discovered in 1994, the cluster, known as M54 in Messier’s famous catalogue, is actually located some 90,000 light years away in the Sagittarius Dwarf Elliptical Galaxy, about three times farther than Earth is from the center of the Milky Way. But if you wait a while – a very long while – M54 will become part of Earth’s galaxy as the Sagittarius dwarf slowly merges with the larger body. This photograph of M54 was taken in 2011 by the Hubble Space Telescope’s Advanced Camera for Surveys.
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VST captures 615-megapixel image of open cluster Messier 18
Messier 18 is the small smattering of bright blue stars upper left of centre in this small-scale version of the original mammoth 30,577 x 20,108 pixel ESO image captured by the OmegaCAM camera attached to the VLT Survey Telescope (VST), located at the European Southern Observatory’s Paranal Observatory in Chile.