The Virgo Cluster is a large
cluster of galaxies whose center is
53.8 ± 0.3Mly (16.5 ± 0.1
Mpc)[2] away in the
constellationVirgo. Comprising approximately 1,300 (and possibly up to 2,000) member galaxies,[3] the cluster forms the heart of the larger
Virgo Supercluster, of which the
Local Group (containing our
Milky Way galaxy) is a 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.[4]
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.[6]
Characteristics
The cluster is a fairly
heterogeneous mixture of
spiral and
elliptical galaxies.[7] As of 2004[update], it is believed that the spiral galaxies of the cluster are distributed in an oblong
prolatefilament, approximately four times as long as it is wide, stretching along the line of sight from the
Milky Way.[8] The elliptical galaxies are more centrally concentrated than the spiral galaxies.[9]
The cluster is an aggregate 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.[10] Notably, the giant
elliptical galaxy M87 contains a
supermassive black hole, whose
event horizon was observed by the
Event Horizon Telescope Collaboration in 2019.[11][12]
Of all of the subclumps, Virgo A, formed by a mixture of
elliptical,
lenticular, and (usually) gas-poor
spiral galaxies,[13] is the dominant one, with a mass of approximately 1014M☉, which is approximately an order of magnitude larger than the other two subclumps.[14]
The three subgroups are in the process of merging to form a larger single cluster[14] 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,[15] 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.[16] This strongly suggests the Virgo cluster is a dynamically young cluster that is still forming.[15]
Other two nearby aggregations known as M Cloud, W Cloud, and W' Cloud[10] seem to be background systems independent of the main cluster.[15]
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.
Molecular gasses in Virgo Cluster has been swept away by a huge cosmic broom that is preventing nearby galaxies from birthing new stars. The actual cause of it has been a long standing mystery in
astrophysics. According to scientists, it occurs because of the extreme environment of the Virgo Cluster.[17]
Below is a table of bright or notable objects in the cluster and their subunit (subcluster). Note that in some cases a galaxy may be considered in a different subunit by other researchers (sources:[10][15][27][28])
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.
Fainter galaxies within the cluster are usually known by their numbers in the Virgo Cluster Catalog, particularly members of the numerous dwarf galaxy population.[29]
^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.[5]
^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.
S2CID16483538.
^
Chamaraux, P.; Balkowski, C.; Gerard, E. (1980). "The H I deficiency of the Virgo cluster spirals". Astronomy & Astrophysics. 83 (1–2): 38–51.
Bibcode:
1980A&A....83...38C.
^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.