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Astronomers using the NASA/ESA Hubble Space Telescope have captured a striking image of NGC 2005, a globular cluster located 162,000 light-years away from Earth in the constellation of Dorado.
This Hubble image shows the globular cluster NGC 2005. The color composite was assembled from images taken in visible and near-infrared light by Hubble’s Wide Field Camera 3 (WFC3). It is based on data obtained through three filters. The color results from assigning different hues to each monochromatic image associated with an individual filter. Image credit: NASA / ESA / Hubble / F. Niederhofer / L. Girardi.
Globular clusters are densely-packed systems of very ancient stars, gravitationally bound into a single structure about 100-200 light-years across.
They contain hundreds of thousands or perhaps a million stars. The large mass in the rich stellar center of a cluster pulls the stars inward to form a ball of stars. The word globulus, from which these clusters take their name, is Latin for small sphere.
Globular clusters are among the oldest known objects in the Universe and are relics of the first epochs of galaxy formation.
Of the 150 globular clusters belonging to the Milky Way, about 70 lie within 13,000 light-years from the Galactic center where their density tends to peak.
“Studying globular clusters in space can be a little like studying fossils on Earth: where fossils give insights into the characteristics of ancient plants and animals, globular clusters illuminate the characteristics of ancient stars,” the Hubble astronomers said.
“Current theories of galaxy evolution predict that galaxies merge with one another.”
“It is widely thought that the relatively large galaxies that we observe in the modern Universe were formed via the merging of smaller galaxies.”
“If this is correct, then astronomers would expect to see evidence that the most ancient stars in nearby galaxies originated in different galactic environments.”
“As globular clusters are known to contain ancient stars, and because of their stability, they are an excellent laboratory to test this hypothesis.”
“NGC 2005 is such a globular cluster, and its very existence has provided evidence to support the theory of galaxy evolution via mergers.”
NGC 2005 is located about 750 light-years from the heart of the Large Magellanic Cloud, the Milky Way’s largest satellite galaxy.
Also known as ESO 56-138, this globular cluster was discovered on September 24, 1826 by the Scottish astronomer James Dunlop.
“The stars in NGC 2005 have a chemical composition that is distinct from the stars in the Large Magellanic Cloud around it,” the researchers said.
“This suggests that the Large Magellanic Cloud underwent a merger with another galaxy somewhere in its history.”
“That other galaxy has long-since merged and otherwise dispersed, but NGC 2005 remains behind as an ancient witness to the long-past merger.”
