Messier 84 or M84, also known as NGC 4374, is a giant elliptical or

lenticular galaxy A lenticular galaxy (denoted S0) is a Galaxy morphological classification, type of galaxy intermediate between an elliptical galaxy, elliptical (denoted E) and a spiral galaxy in galaxy morphological classification schemes. It contains a large-s ...

in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellati ...

Virgo Virgo may refer to: Arts and entertainment * Virgo (film), a 1970 Egyptian film * Virgo (character), several Marvel Comics characters * Virgo Asmita, a character in the manga ''Saint Seiya: The Lost Canvas'' * ''Virgo'' (album), by Virgo Four, ...

Charles Messier Charles Messier (; 26 June 1730 – 12 April 1817) was a French astronomer. He published an astronomical catalogue consisting of 110 nebulae and star clusters, which came to be known as the ''Messier objects'', referred to with th ...

discovered the object in 1781 in a systematic search for "nebulous objects" in the night sky. It is the 84th object in the

Messier Catalogue The Messier objects are a set of 110 astronomical objects catalogued by the French astronomer Charles Messier in his ' (''Catalogue of Nebulae and Star Clusters''). Because Messier was interested only in finding comets, he created a list of thos ...

and in the heavily populated core of the

Virgo Cluster of galaxies The Virgo Cluster is a cluster of galaxies whose center is 53.8 ± 0.3 Mly (16.5 ± 0.1 Mpc) away in the Virgo constellation. Comprising approximately 1,300 (and possibly up to 2,000) member galaxies, the cluster forms the heart of the larger V ...

, part of the

local supercluster The Local Supercluster (LSC or LS), or Virgo Supercluster is a formerly defined supercluster containing the Virgo Cluster and Local Group, which itself contains the Milky Way and Andromeda galaxies, as well as others. At least 100 galaxy groups a ...

. This galaxy has morphological classification E1, denoting it has

flattening Flattening is a measure of the compression of a circle or sphere along a diameter to form an ellipse or an ellipsoid of revolution (spheroid) respectively. Other terms used are ellipticity, or oblateness. The usual notation for flattening is f ...

of about 10%. The

extinction Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

-corrected total

luminosity Luminosity is an absolute measure of radiated electromagnetic radiation, electromagnetic energy per unit time, and is synonymous with the radiant power emitted by a light-emitting object. In astronomy, luminosity is the total amount of electroma ...

in the visual band is about . The central mass-to-light ratio is 6.5, which, to a limit, steadily increases away from the core. The visible galaxy is surrounded by a massive

dark matter In astronomy, dark matter is an invisible and hypothetical form of matter that does not interact with light or other electromagnetic radiation. Dark matter is implied by gravity, gravitational effects that cannot be explained by general relat ...

halo. Radio observations and

Hubble Space Telescope The Hubble Space Telescope (HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the Orbiting Solar Observatory, first space telescope, but it is one of the largest and most ...

images of M84 have revealed two jets of matter shooting out from its center as well as a disk of rapidly rotating gas and stars indicating the presence of a supermassive

black hole A black hole is a massive, compact astronomical object so dense that its gravity prevents anything from escaping, even light. Albert Einstein's theory of general relativity predicts that a sufficiently compact mass will form a black hole. Th ...

. It also has a few young stars and

star cluster A star cluster is a group of stars held together by self-gravitation. Two main types of star clusters can be distinguished: globular clusters, tight groups of ten thousand to millions of old stars which are gravitationally bound; and open cluster ...

s, indicating

star formation Star formation is the process by which dense regions within molecular clouds in interstellar space—sometimes referred to as "stellar nurseries" or "star-forming regions"—Jeans instability, collapse and form stars. As a branch of astronomy, sta ...

at a very low rate. The number of

globular cluster A globular cluster is a spheroidal conglomeration of stars that is bound together by gravity, with a higher concentration of stars towards its center. It can contain anywhere from tens of thousands to many millions of member stars, all orbiting ...

s is , which is much lower than expected for an elliptical galaxy. Viewed from Earth its half-light radius, relative angular size of its 50% peak of lit zone of the sky, is , thus just over an

arcminute A minute of arc, arcminute (abbreviated as arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of a degree. Since one degree is of a turn, or complete rotation, one arcminute is of a tu ...

Supernovae

Three

supernova A supernova (: supernovae or supernovas) is a powerful and luminous explosion of a star. A supernova occurs during the last stellar evolution, evolutionary stages of a massive star, or when a white dwarf is triggered into runaway nuclear fusion ...

e have been observed in M84: * SN 1957B ( typeIa, mag. 12.5) was discovered by H. S. Gates on 28 April 1957, and independently by Dr. Giuliano Romano on 18 May 1957. * SN 1980I (type Ia, mag. 14) was discovered by M. Rosker on 13 June 1980. Historically, this supernova has been catalogued as belonging to M84, but it may have been in either neighboring galaxy

NGC 4387 NGC may refer to: Companies * NGC Corporation, the name of US electric company Dynegy, Inc. from 1995 to 1998 * National Gas Company of Trinidad and Tobago, a state-owned natural gas company in Trinidad and Tobago * National Grid plc, a former nam ...

or M86. * SN 1991bg (type Ia-pec, mag. 14) was discovered by

Reiki Kushida is a Japanese amateur astronomer, discoverer of supernovae such as 1991bg (the first visual discovery made by a female astronomer), and co-discoverer of 4875 Ingalls, a Flora asteroid from the main-belt. Reiki Kushida is married to astr ...

on 3 December 1991. This supernova has been studied extensively as a peculiar and underluminous Type Ia, and is now used as a template, with similar events being classified as ''Type Ia-91bg-like''. This high rate of supernovae is rare for elliptical galaxies, which may indicate there is a population of stars of intermediate age in M84. M84map

References and footnotes

External links

''StarDate'': M84 Fact Sheet

{{DEFAULTSORT:Messier 084 Elliptical galaxies Lenticular galaxies Virgo Cluster Virgo (constellation)

084 Area codes 084 and 086 are Nigerian telephone area codes serving the cities of Port Harcourt and Ahoada in Rivers State. They fall under the Southeast Zone in the National Numbering Plan (NNP) restructured in 2003. When in Port Harcourt or Ahoad ...

NGC objects 07494 40455 17810318 Discoveries by Charles Messier Radio galaxies

272 __NOTOC__ Year 272 ( CCLXXII) was a leap year starting on Monday of the Julian calendar. At the time, it was known as the Year of the Consulship of Postumius and Veldumnianus (or, less frequently, year 1025 ''Ab urbe condita''). The denominati ...

4C objects

Supernovae

See also

References and footnotes

External links