The Virgo Cluster is a cluster of galaxies whose center is 53.8 ± 0.3Mly (16.5 ± 0.1 Mpc)
away in the constellationVirgo. 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 (containing the Milky Way galaxy) is an outlying member. The Local Group actually experiences the mass of the Virgo Supercluster as the Virgocentric flow. It is estimated that the Virgo Cluster's mass is 1.2×1015M☉ 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 galaxyMessier 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.[A]
The cluster subtends a maximum arc of approximately 8 degrees centered in the constellation Virgo. Although some of the cluster's most prominent members can be seen with smaller instruments, a 6 inch telescope will reveal about 160 of the cluster's galaxies on a clear night. Its brightest member is the elliptical galaxyMessier 49; however its most famous member is the elliptical galaxy Messier 87, which is located in the center of the cluster.
Virgo Cluster showing the diffuse light between member galaxies. Messier 87 is the largest galaxy (lower left).
The cluster is a fairly heterogeneous mixture of spirals and ellipticals. As of 2004, it is believed that the spiral galaxies of the cluster are distributed in an oblong prolate filament, approximately four times as long as it is wide, stretching along the line of sight from the Milky Way. The elliptical galaxies are more centrally concentrated than the spiral galaxies.
The cluster is an aggregrate of at least three separate subclumps: Virgo A, centered on M87, a second centered on the galaxy M86, and Virgo B, centered on M49, with some authors including a Virgo C subcluster, centered on the galaxy M60 as well as a LVC (Low Velocity Cloud) subclump, centered on the large spiral galaxy NGC 4216.
Of all of the subclumps, Virgo A, formed by a mixture of elliptical, lenticular, and (usually) gas-poor spiral galaxies, is the dominant one, with a mass of approximately 1014M☉, which is approximately an order of magnitude larger than the other two subclumps.
The three subgroups are in the process of merging to form a larger single cluster and are surrounded by other smaller galaxy clouds, mostly composed of spiral galaxies, known as N Cloud, S Cloud, and Virgo E that are in the process of infalling to merge with them, plus other farther isolated galaxies and galaxy groups (like the galaxy cloud Coma I) that are also attracted by the gravity of Virgo to merge with it in the future. This strongly suggests the Virgo cluster is a dynamically young cluster that is still forming.
Other two nearby aggregations known as M Cloud, W Cloud, and W' Cloud seem to be background systems independent of the main cluster.
The large mass of the cluster is indicated by the high peculiar velocities of many of its galaxies, sometimes as high as 1,600 km/s with respect to the cluster's center.
The Virgo cluster lies within the Virgo Supercluster, and its gravitational effect slows down the nearby galaxies. The large mass of the cluster has the effect of slowing down the recession of the Local Group from the cluster by approximately ten percent.
Below is given a table of bright or notable objects in the Virgo Cluster and the subunit of the cluster in which they are located. Note that in some cases a galaxy may be considered in a different subunit by other researchers (sources:)
Column 1: The name of the galaxy.
Column 2: The right ascension for epoch 2000.
Column 3: The declination for epoch 2000.
Column 4: The blue apparent magnitude of the galaxy.
^Following the entry for M91 in the Connoissance des Temps for 1784, Messier added the following note:
The constellation of Virgo, & especially the northern Wing is one of the constellations which encloses the most Nebulae: this Catalog contains thirteen which have been determined: viz. Nos. 49, 58, 59, 60, 61, 84, 85, 86, 87, 88, 89, 90, & 91. All these nebulae appear to be without stars: one can see them only in a very good sky, & near their meridian passage. Most of these nebulae have been pointed to me by Mr. Méchain.
^Mei, Simona; Blakeslee, John P.; Côté, Patrick; Tonry, John L.; West, Michael J.; Ferrarese, Laura; Jordán, Andrés; Peng, Eric W.; Anthony, André; Merritt, Davi (2007). "The ACS Virgo Cluster Survey. XIII. SBF Distance Catalog and the Three-dimensional Structure of the Virgo Cluster". The Astrophysical Journal. 655 (1): 144–162. arXiv:astro-ph/0702510. Bibcode:2007ApJ...655..144M. doi:10.1086/509598.
^Lea, S. M.; Mushotzky, R.; Holt, S. S. (1982). "Einstein Observatory solid state spectrometer observations of M87 and the Virgo cluster". Astrophysical Journal. 262 (1): 24–32. Bibcode:1982ApJ...262...24L. doi:10.1086/160392.
^Takamiya, Marianne; West, Michael; Côté, Patrick; Jordán, Andrés; Peng, Eric; Ferrarese, Laura (2009). "IGCs in the Virgo Cluster". Globular Clusters – Guides to Galaxies, Eso Astrophysics Symposia, Volume. Eso Astrophysics Symposia: 361–365. Bibcode:2009gcgg.book..361T. doi:10.1007/978-3-540-76961-3_83. ISBN 978-3-540-76960-6.
^Durrell, Patrick R.; Accetta, K.; Feldmeier, J. J.; Mihos, J. C.; Ciardullo, R.; Peng, E. W.; Members of the NGVS team (2010). "Searching for Intracluster Globular Clusters in the Virgo Cluster". Bulletin of the American Astronomical Society. 42: 567. Bibcode:2010AAS...21547814D.
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