The Virgo Galaxy Cluster
Object Type: Galaxy Cluster
Exposure 60 minutes
The Virgo Cluster (VC) is a cluster of galaxies whose center is 53.8 ± 0.3 Mly (16.5 ± 0.1 Mpc) away in the constellation Virgo. Comprising approximately 1300 (and possibly up to 2000) member galaxies, the cluster forms the heart of the larger Virgo Supercluster, of which the Local Group (LG) is an outlying member. However, the LG experiences the mass of the VC as the Virgocentric flow. It is estimated that the VC's mass is 1.2×1015 M☉ out to 8 degrees of the cluster's center or a radius of about 2.2 Mpc.
Many of the brighter galaxies in this cluster, including the giant elliptical galaxy Messier 87, were discovered in the late 1770s and early 1780s and subsequently included in Charles Messier's catalogue of non-cometary fuzzy objects. Described by Messier as nebulae without stars, their true nature was not recognized until the 1920s.
The cluster subtends a maximum arc of approximately 8 degrees centered in the constellation Virgo. Many of the member galaxies of the cluster are visible with a small telescope. Its brightest member is the elliptical galaxy Messier 49; however its most famous member is the also elliptical galaxy Messier 87, that unlike the former is located in the center of the cluster.
As with many other rich galaxy clusters, Virgo's intracluster medium is filled with a hot, rarefied plasma at temperatures of 30 million Kelvin that emits X-Rays, and within it can be found a large number ofintergalactic stars (up to 10% of the stars in the cluster), including some planetary nebulae, that it's theorized were expelled from their home galaxies on interactions with other galaxies, as well as someglobular clusters, possibly stripped off dwarf galaxies, and even at least one star formation region.