NGC 4874 and Its 30,000 Globulars
An elliptical supergiant in the constellation Coma Berenices guarded by an enormous number of globular clusters
The Coma cluster in the constellation Coma Berenice is the most massive in the local Universe. It comprises some 20,000 galaxies, over 1,000 of which have been individually cataloged.
This immense archipelago of galaxies, whose total mass is estimated at 2.7 million billion solar masses, is dominated by two supergiant elliptical galaxies, NGC 4889 and NGC 4874. In the image above, acquired with the Hubble Space Telescope, one of these two monsters of the sky is visible. It is NGC 4874, the almost spherical galaxy on the right of the image, clearly larger than all the neighbors.
At a distance of about 355 million light-years from Earth, NGC 4874 has a diameter of around 1 million light-years (ten times that of the Milky Way) and a mass estimated at 1,000 billion solar masses.
This real giant is surrounded by an immense swarm of globular clusters, dense spheroidal gatherings of mostly very ancient stars, possible remnants of dwarf galaxies “swallowed” in the distant past by NGC 4874. Indeed, some of these clusters are dwarf galaxies classified as UCD (Ultra-Compact Dwarf), with diameters estimated in the order of 200 light-years.
