View source for Messier 87

{{Short description|Elliptical galaxy in the constellation Virgo}}
{{Featured article}}
{{Use dmy dates|date=March 2020}}
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{{Infobox galaxy
| name       = Messier 87
| image      = File:Messier 87 Hubble WikiSky.jpg
| caption    = Messier 87, with the blue [[astrophysical jet|plasma jet]] of its [[active galactic nucleus|galactic core]] clearly visible ([[compositing|composite image]] of observations by the [[Hubble Space Telescope]] in [[visible spectrum|visible]] and [[infrared]] light)
| alt        = Visual wavelength image of Messier&nbsp;87 with bright core, jet and globular clusters
| epoch      = [[Epoch (astronomy)#Julian years and J2000|J2000]]
| constellation name   = [[Virgo (constellation)|Virgo]]
| ra         = {{RA|12|30|49.42338}}<ref name=aaa493_1/>
| dec        = {{DEC|+12|23|28.0439}}<ref name=aaa493_1/>
| size_v     = 7.2 × 6.8 [[Minute of arc|arcmin]]<ref name=luginbuhl_skiff98/>
| size       = {{cvt|40.55|kpc|ly|sigfig=3|lk=on}}<ref name=ned/><ref name=RC3>{{cite book | url=https://ui.adsabs.harvard.edu/abs/1991rc3..book.....D | bibcode=1991rc3..book.....D | year=1991 | title=Third Reference Catalogue of Bright Galaxies | last1=De Vaucouleurs | first1=Gerard | last2=De Vaucouleurs | first2=Antoinette | last3=Corwin | first3=Herold G. | last4=Buta | first4=Ronald J. | last5=Paturel | first5=Georges | last6=Fouque | first6=Pascal }}</ref><br />(25.0 mag/arcsec<sup>2</sup> B-band isophote){{efn|name=halo|Size quoted refers to the diameter directly measured by the 25.0 mag/arcsec<sup>2</sup> isophote at the B-band. The galaxy has a much diffuse and extensive halo extending up to {{cvt|300|kpc|ly|sigfig=2|abbr=off}}.<ref name=aaa502_3/>}}
| appmag_v   = 8.6<ref>{{cite web |url=https://messier.seds.org/m/m087.html |title=Messier 87 |access-date=30 April 2022 |website=SEDS Messier Catalog}}</ref>
| type       = E+0-1 pec, NLRG Sy<ref name=ned/>
| h_radial_v = 1,284 ± 5 [[Metre per second|km/s]]<ref name=2011MNRAS/>
| z          = 0.00428 ± 0.00002<ref name=2011MNRAS/>
| gal_v      =
| gv_err     =
| dist_ly    = {{cvt|16.4 ± 0.5|Mpc|Mly|lk=on}}<ref name=aaa524_1/>
| names      = Virgo&nbsp;A, Virgo&nbsp;X-1, [[New General Catalogue|NGC]]&nbsp;4486, [[Uppsala General Catalogue|UGC]]&nbsp;7654, [[Principal Galaxies Catalogue|PGC]]&nbsp;41361, VCC&nbsp;1316, [[Atlas of Peculiar Galaxies|Arp]]&nbsp;152, [[Third Cambridge Catalogue of Radio Sources|3C]]&nbsp;274,<ref name=ned/> 3U&nbsp;1228+12.<ref name=mnras170/>
}}

'''Messier&nbsp;87''' (also known as '''Virgo&nbsp;A''' or '''NGC&nbsp;4486''', generally abbreviated to '''M87''') is a [[Type-cD galaxy|supergiant]] [[elliptical galaxy|elliptical]] [[galaxy]] in the [[constellation]] [[Virgo (constellation)|Virgo]] that contains several trillion stars. One of the [[List of largest galaxies|largest and most massive galaxies]] in the local universe,{{efn|1="Local universe" is not a strictly defined term, but it is often taken as that part of the universe out to distances between about 50&nbsp;million to a billion [[light-year]]s.<ref name=localuniverse_1/><ref name=localuniverse_2/><ref name=localuniverse_3/>|name=|group=}} it has a large population of [[globular cluster]]s—about 15,000 compared with the 150–200 orbiting the [[Milky Way]]—and a jet of energetic [[plasma (physics)|plasma]] that originates at the core and extends at least {{convert|1500|pc|lk=on|abbr=off}}, traveling at a [[relativistic speed]]. It is one of the brightest radio sources in the sky and a popular target for both amateur and professional [[astronomer]]s.

The French astronomer [[Charles Messier]] discovered M87 in 1781, and cataloged it as a [[nebula]]. M87 is about {{convert|16.4|e6pc|e6ly|abbr=off}} from Earth and is the second-brightest galaxy within the northern [[Virgo Cluster]], having many [[satellite galaxies]]. Unlike a disk-shaped [[spiral galaxy]], M87 has no distinctive [[dust lane]]s. Instead, it has an almost featureless, [[ellipsoid]]al shape typical of most [[giant elliptical galaxy|giant elliptical galaxies]], diminishing in [[luminosity]] with distance from the center. Forming around one-sixth of its mass, M87's [[star]]s have a nearly spherically symmetric distribution. Their population density decreases with increasing distance from the core. It has an active [[supermassive black hole]] at its core, which forms the primary component of an [[active galactic nucleus]]. The black hole was imaged using data collected in 2017 by the [[Event Horizon Telescope]] (EHT), with a final, processed image released on 10&nbsp;April 2019.<ref name="NYT-20240124" /> In March&nbsp;2021, the EHT Collaboration presented, for the first time, a [[Polarization (waves)|polarized-based image]] of the black hole which may help better reveal the forces giving rise to [[quasar]]s.<ref name="NYT-20210324">{{cite news |last=Overbye |first=Dennis |author-link=Dennis Overbye |date=24 March 2021 |title=The most intimate portrait yet of a black hole – Two years of analyzing the polarized light from a galaxy's giant black hole has given scientists a glimpse at how quasars might arise |newspaper=[[The New York Times]] |url=https://www.nytimes.com/2021/03/24/science/astronomy-messier-87-black-hole.html |archive-url=https://ghostarchive.org/archive/20211228/https://www.nytimes.com/2021/03/24/science/astronomy-messier-87-black-hole.html |archive-date=2021-12-28 |url-access=limited |access-date=25 March 2021 }}{{cbignore}}</ref>

The galaxy is a strong source of multi-wavelength radiation, particularly [[radio wave]]s. It has an [[isophote|isophotal]] diameter of {{convert|40.55|kpc|ly|sigfig=3|abbr=off}}, with a diffuse galactic envelope that extends to a radius of about {{convert|150|kpc|ly|abbr=off}}, where it is truncated—possibly by an [[Galaxy merger|encounter]] with another galaxy. Its [[interstellar medium]] consists of diffuse gas enriched by elements emitted from [[evolved star]]s.

==Observation history==
In 1781, the French astronomer Charles Messier published a [[Messier object|catalogue]] of 103 objects that had a nebulous appearance as part of a list intended to identify objects that might otherwise be confused with [[comet]]s. In subsequent use, each catalogue entry was prefixed with an "M". Thus, M87 was the eighty-seventh object listed in Messier's catalogue.<ref name=basu03/> During the 1880s, the object was included as NGC&nbsp;4486 in the ''[[New General Catalogue]]'' of nebulae and star clusters assembled by the Danish-Irish astronomer [[John Louis Emil Dreyer|John Dreyer]], which he based primarily on the observations of the English astronomer [[John Herschel]].<ref name=mras49/>

In 1918, the American astronomer [[Heber Doust Curtis|Heber Curtis]] of [[Lick Observatory]] noted M87's lack of a spiral structure and observed a "curious straight ray ... apparently connected with the nucleus by a thin line of matter." The ray appeared brightest near the galactic center.<ref name=plo13/> The following year, [[supernova]] SN 1919A within M87 reached a peak [[photographic magnitude]] of 11.5, although this event was not reported until photographic plates were examined by the Russian astronomer Innokentii A. Balanowski in 1922.<ref name=pasp35_207/><ref name=sa24/>

===Identification as a galaxy===
[[File:HubbleTuningFork.jpg|thumb|In Hubble's [[Galaxy morphological classification|galaxy classification scheme]], M87 is an E0&nbsp;galaxy. |alt= Hubble classified galaxies according to their shape: ellipticals, lenticulars and spirals. Ellipticals and spirals have further categories.]]
In 1922, the American astronomer [[Edwin Hubble]] categorized M87 as one of the brighter globular nebulae, as it lacked any spiral structure, but like spiral nebulae, appeared to belong to the family of non-galactic nebulae.<ref name=apj56/> In 1926 he produced a new categorization, distinguishing extragalactic from galactic nebulae, the former being independent star systems. M87 was [[Galaxy morphological classification|classified]] as a type of elliptical extragalactic nebula with no apparent elongation (class E0).<ref name=apj64/>

In 1931, Hubble described M87 as a member of the Virgo Cluster, and gave a provisional estimate of {{convert|1.8|e6pc|e6ly|abbr=off}} from Earth. It was then the only known elliptical nebula for which individual stars could be [[optical resolution|resolved]], although it was pointed out that globular clusters would be indistinguishable from individual stars at such distances.<ref name=apj74/> In his 1936 ''The Realm of the Nebulae'', Hubble examines the terminology of the day; some astronomers labeled extragalactic nebulae as ''external galaxies'' on the basis that they were stellar systems at far distances from our own galaxy, while others preferred the conventional term ''extragalactic nebulae'', as ''galaxy'' was at that time a synonym for the Milky Way.<ref name=Hubble-1936/> M87 continued to be labelled as an extragalactic nebula at least until 1954.<ref name=apj119/><ref name=apj124_416/>

===Modern research===
In 1947, a prominent [[Radio astronomy|radio]] source, Virgo&nbsp;A, was identified with errors in its measured position that overlapped the location of M87.<ref name="ajsra3"/> The source was confirmed to be M87 by 1953, and the linear [[relativistic jet]] emerging from the core of the galaxy was suggested as the cause. This jet extended from the core at a [[position angle]] of 260° to an [[angular distance]] of 20[[arcsecond|″]] with an angular width of 2″<!-- context: what distances in parsecs do these angles represent at the distance of M87? -->.<ref name="apj119"/> In 1969–1970, a strong component of the radio emission was found to closely align with the optical source of the jet.<ref name="mnras170"/>
In 1966, the [[United States Naval Research Laboratory]]'s [[Aerobee]]&nbsp;150 rocket identified Virgo&nbsp;X-1, the first X-ray source in Virgo.<ref name=HEASARC1965/><ref name=charles95/> The Aerobee rocket launched from [[White Sands Missile Range]] on 7&nbsp;July 1967 yielded further evidence that the source of Virgo&nbsp;X-1 was the radio galaxy M87.<ref name=bradt68/> Subsequent X-ray observations by the [[High Energy Astronomy Observatory 1|HEAO&nbsp;1]] and [[Einstein Observatory]] showed a complex source that included the active galactic nucleus of M87.<ref name=apj262/> However, there is little central concentration of the X-ray emission.<ref name=mnras170/>

M87 has been an important testing ground for techniques that measure the masses of central supermassive black holes in galaxies. In 1978, [[stellar-dynamical]] modeling of the mass distribution in M87 gave evidence for a central mass of five&nbsp;billion {{solar mass|link=y}} [[solar mass]]es.<ref name=Sargent1978/> After the installation of the [[COSTAR]] corrective-optics module in the [[Hubble Space Telescope]] in 1993, the Hubble [[Faint Object Spectrograph]] (FOS) was used to measure the [[rotation velocity]] of the ionized gas disk at the center of M87, as an "early release observation" designed to test the scientific performance of the post-repair Hubble instruments. The FOS data indicated a central black hole mass of 2.4&nbsp;billion {{solar mass|link=y}}, with 30% uncertainty.<ref name=Harms1994/> Globular clusters within M87 have been used to calibrate metallicity relations as well.<ref>{{cite journal |author1=Forte, Juan C. |author2=Faifer, Favio R. |author3=Vega, E. Irene |author4=Bassino, Lilia P. |author5=Smith Castelli, Analía V. |author6=Cellone, Sergio A. |author7=Geisler, Douglas |date=11 May 2013 |title=Multicolour–metallicity relations from globular clusters in NGC&nbsp;4486 (M87) |journal=Monthly Notices of the Royal Astronomical Society |volume=431 |issue=2 |pages=1405–1416 |doi=10.1093/mnras/stt263|doi-access=free |arxiv=1302.3154 }}</ref>

M87 was observed by the [[Event Horizon Telescope]] (EHT) during much of 2017.{{refn| {{cite journal |date=10 April 2019 |title=[whole issue] |journal=Astrophysical Journal Letters |volume=875 |issue=1}} was dedicated to the results, published six [[open-access]] papers.<ref name=AJL875-1/> }} The [[event horizon]] of the black hole at the center was directly imaged by the EHT,<ref name=BHImage/> then revealed in a press conference on the issue date stated, filtering out from this the first image of a black hole's shadow.<ref name=EHT2019/>

==Visibility==
[[File:Virgo constellation map.svg|thumb|Area in constellation Virgo around M87]]

M87 is near a high [[declination]] limit of the Virgo constellation, abutting [[Coma Berenices]]. It lies along the line between the stars [[Epsilon Virginis]] and [[Denebola]] (Beta [[Leo (constellation)|Leo]]nis).{{efn|1= Epsilon Virginis is at celestial coordinates {{mvar|α}}=13ʰ02ᵐ, {{mvar|δ}}=+10°57′; Denebola is at {{mvar|α}}=11ʰ49ᵐ, {{mvar|δ}}=+14°34′. The midpoint of the pair is at {{mvar|α}}=12ʰ16ᵐ, {{mvar|δ}}=12°45′. Compare to the coordinates of Messier&nbsp;87: {{mvar|α}}=12ʰ31ᵐ, {{mvar|δ}}=+12°23′&nbsp;.}} The galaxy can be observed using a small telescope with a {{cvt|6|cm}} [[aperture]], extending across an angular area of {{nobr| 7.2 × 6.8 [[arcminutes]] }} at a [[surface brightness]] of 12.9, with a very bright, 45&nbsp;[[arcsecond]] core.<ref name=luginbuhl_skiff98/> Viewing the jet is a challenge without the aid of photography.<ref name=cooke2005/> Before 1991, the Ukrainian-American astronomer [[Otto Struve]] was the only person known to have seen the jet visually, using the {{cvt|254|cm}} [[Mount Wilson Observatory|Hooker telescope]].<ref name=clark90/> In more recent years it has been observed in larger amateur telescopes under excellent conditions.<ref name=astromall/>

==Properties==
In the modified [[Hubble sequence]] [[galaxy morphological classification]] scheme of the French astronomer [[Gérard de Vaucouleurs]], M87 is categorized as an E0p galaxy. "E0" designates an elliptical galaxy that displays no flattening—that is, it appears spherical.<ref name=jass4_1/> A "p" suffix indicates a [[peculiar galaxy]] that does not fit cleanly into the classification scheme; in this case, the peculiarity is the presence of the jet emerging from the core.<ref name=jass4_1/><ref name=jones_lambourne04/> In the [[Galaxy morphological classification#Yerkes (or Morgan) scheme|Yerkes (Morgan) scheme]], M87 is classified as a [[type-cD galaxy]].<ref name=aj121_6/><ref name=mnras377_1/> A D&nbsp;galaxy has an elliptical-like nucleus surrounded by an extensive, dustless, diffuse envelope. A D&nbsp;type supergiant is called a cD&nbsp;galaxy.<ref name=apj209/><ref name=whitmore89/>

The distance to M87 has been estimated using several independent techniques. These include measurement of the luminosity of [[planetary nebula]]e, comparison with nearby galaxies whose distance is estimated using [[Cosmic distance ladder|standard candles]] such as [[cepheid variable]]s, the linear size distribution of [[globular cluster]]s,{{efn|1=This yields a distance of {{Convert|16.4|+/-|2.3|Mpc|e6ly|abbr=off|sigfig=3}}.<ref name=aaa524_1/>}} and the [[tip of the red-giant branch]] method using individually resolved [[red giant]] stars.{{efn|1=This yields a distance of {{Convert|16.7|+/-|0.9|Mpc|e6ly|abbr=off|sigfig=3}}.<ref name=aaa524_1/>}} These measurements are consistent with each other, and their [[Weighted arithmetic mean|weighted average]] yields a distance estimate of {{Convert|16.4|+/-|0.5|Mpc|e6ly|abbr=off|sigfig=3}}.<ref name=aaa524_1/>

{| class="wikitable" style="float: right; text-align: center; margin-left: 0.5em;"
|+ Enclosed mass
|- style="background-color: #eeeeee;"
| '''Radius'''<br />kpc
| '''Mass'''<br />×{{Solar mass|{{10^|12}}|link=yes}}
|-
| 32 || 2.4<ref name=apj643_1/>
|-
| 44 || 3.0<ref name=apj486/>
|-
| 47 || 5.7<ref name=apj729_2/>
|-
| 50 || 6.0<ref name=apj106_6/>
|}

[[File:Galactic Chromodynamics.jpg|thumb|left|Stellar velocity map of the central region of M87, showing the motion of stars relative to Earth: {{legend|#f61003|away}}{{legend|#ff8d03}}{{legend|#fbfe00}}{{legend|#19ec03}}{{legend|#74ecfe}}{{legend|#0001d8|towards}} The image shows a slight rotation in the vertical plane (the lower right moving toward earth, the upper left moving away), showing that M87 is rotating slowly.<ref name=gcd/><ref name=vel_map/>|alt=stellar velocities in M87 show a slow rotation]]

M87 is one of the most massive galaxies in the local Universe. Its diameter is estimated at 132,000&nbsp;light-years, which is approximately 51% larger than that of the Milky Way.<ref name=ned/><ref name=RC3/> As an elliptical galaxy, the galaxy is a spheroid rather than a flattened disc, accounting for the substantially larger mass of M87. Within a radius of {{convert|32|kpc|ly|abbr=off}}, the mass is {{val|2.4|0.6|e=12}} times the mass of the Sun,<ref name=apj643_1/> which is double the mass of the [[Milky Way]] galaxy.<ref name=mnras364/> As with other galaxies, only a [[Dark matter|fraction of this mass is in the form of stars]]: M87 has an estimated mass to luminosity ratio of {{nowrap|6.3 ± 0.8}}; that is, only about one part in six of the galaxy's mass is in the form of stars that radiate energy.<ref name="apj700_2_1690"/> This ratio varies from 5 to 30, approximately [[Proportionality (mathematics)|in proportion]] to {{mvar|r}}{{sup|1.7}} in the region of {{Convert|9|-|40|kpc|ly|abbr=off}} from the core.<ref name=apj486/> The total mass of M87 may be 200&nbsp;times that of the Milky Way.<ref name=leverington00/>

The galaxy experiences an infall of gas at the rate of two to three solar masses per year, most of which may be accreted onto the core region.<ref name=aj86/> The extended stellar envelope of this galaxy reaches a radius of about {{Convert|150|kpc|ly|abbr=off}},<ref name=aaa502_3/> compared with about {{Convert|100|kpc|ly|abbr=off}} for the Milky Way.<ref name=science287_5450_79/> Beyond that distance the outer edge of the galaxy has been truncated by some means; possibly by an earlier encounter with another galaxy.<ref name=aaa502_3/><ref name=klotz090608/> There is evidence of linear [[Stellar kinematics|streams of stars]] to the northwest of the galaxy, which may have been created by [[tidal stripping]] of orbiting galaxies or by small [[satellite galaxies]] falling in toward M87.<ref name=janowiecki10/> Moreover, a filament of hot, ionized gas in the northeastern outer part of the galaxy may be the remnant of a small, gas-rich galaxy that was disrupted by M87 and could be feeding its active nucleus.<ref name=aa361_1/> M87 is estimated to have at least 50&nbsp;satellite galaxies, including [[NGC 4486B]] and [[NGC 4478]].<ref name="oldham072016"/><ref name="Fischer1998"/>

The spectrum of the nuclear region of M87 shows the [[emission line]]s of various ions, including [[hydrogen]] (HI, HII), [[helium]] (HeI), [[oxygen]] (OI, OII, OIII), [[nitrogen]] (NI), [[magnesium]] (MgII), and [[sulfur]] (SII). The line intensities for weakly ionized atoms (such as neutral [[atomic oxygen]], OI) are stronger than those of strongly ionized atoms (such as [[doubly ionized oxygen]], OIII). A galactic nucleus with such spectral properties is termed a LINER, for "[[low-ionization nuclear emission-line region]]".<ref name=Tsvetanov1999/><ref name=dopita1997/> The mechanism and source of weak-line-dominated ionization in LINERs and M87 are under debate. Possible causes include shock-induced excitation in the outer parts of the disk<ref name=Tsvetanov1999/><ref name=dopita1997/> or [[photoionization]] in the inner region powered by the jet.<ref name=sabra2003/>

Elliptical galaxies such as M87 are believed to form as the result of one or more mergers of smaller galaxies.<ref name=dehnen1997/> They generally contain relatively little cold [[Interstellar medium|interstellar gas]] (in comparison with spiral galaxies) and they are populated mostly by old stars, with little or no ongoing star formation. M87's elliptical shape is maintained by the random orbital motions of its constituent stars, in contrast to the more orderly rotational motions found in a [[spiral galaxy]] such as the Milky Way.<ref name=steinicke_jakiel2007/> Using the [[Very Large Telescope]] to study the motions of about 300 planetary nebulae, astronomers have determined that M87 absorbed a medium-sized star-forming spiral galaxy over the last billion years. This has resulted in the addition of some younger, bluer stars to M87. The distinctive spectral properties of the planetary nebulae allowed astronomers to discover a chevron-like structure in M87's halo which was produced by the incomplete [[Phase space|phase-space]] mixing of a disrupted galaxy.<ref name=ggsg/><ref name="Halo Accretion"/>
{{clear}}

==Components==
===Supermassive black hole M87*===
{{multiple image
| align             = center
| direction         = horizontal
| total_width       = 
| image1            = Black hole - Messier 87 crop max res.jpg
| caption1          = The [[Event Horizon Telescope]] image of the core of M87 using 1.3&nbsp;mm [[microwaves]]. The central dark spot is the shadow of M87* and is larger than the black hole's [[event horizon]].
| width1            = 260
| alt               = A dark spot surrounded by doughnut shaped orange-yellow ring
| image2            = A view of the M87 supermassive black hole in polarised light.tif
| caption2          = A view of the M87* supermassive black hole released by the Event Horizon Telescope Collaboration with lines overlaid to mark the orientation of polarization of the magnetic field
| width2            = 257
| image3            = A view of the jet and shadow of M87’s black hole (eso2305a).jpg
| caption3          = A view of the jet and shadow of M87's black hole. Observations from the Global Millimetre VLBI Array (GMVA), the Atacama Large Millimeter/submillimeter Array (ALMA), and the Greenland Telescope.<ref name="SD-20230707">{{cite news |author=CAS |title=Black Hole Unmasked: Astronomers Capture First Image of Accretion Ring and Relativistic Jet |url=https://scitechdaily.com/black-hole-unmasked-astronomers-capture-first-image-of-accretion-ring-and-relativistic-jet/?expand_article=1 |date=7 July 2023 |work=[[SciTech (magazine)|SciTechDaily]] |url-status=live |archive-url=https://archive.today/20230708141152/https://scitechdaily.com/black-hole-unmasked-astronomers-capture-first-image-of-accretion-ring-and-relativistic-jet/?expand_article=1 |archive-date=8 July 2023 |access-date=8 July 2023 }}</ref>
| width3            = 335
}}

The core of the galaxy contains a [[supermassive black hole]] (SMBH), designated M87*,<ref name=AJL875-1/><ref name="NS-name">{{cite magazine |last=Lu |first=Donna |date=12 April 2019 |title=How do you name a black hole? It is actually pretty complicated |magazine=[[New Scientist]] |location=London, UK |url= https://www.newscientist.com/article/2199578-how-do-you-name-a-black-hole-it-is-actually-pretty-complicated/ |access-date=12 April 2019 |quote={{-'}}For the case of M87*, which is the designation of this black hole, a (very nice) name has been proposed, but it has not received an official IAU approval,' says Christensen.}}</ref><ref name="NYT-20240124">{{cite news |last=Overbye |first=Dennis |authorlink=Dennis Overbye |title=That Famous Black Hole Gets a Second Look - Repeated studies of the supermassive black hole in the galaxy Messier 87 confirm that it continues to act as Einstein's theory predicted it would. |url=https://www.nytimes.com/2024/01/24/science/space/black-holes-photography-m87.html |date=24 January 2024 |work=[[The New York Times]] |url-status=live |archiveurl=https://archive.today/20240124200523/https://www.nytimes.com/2024/01/24/science/space/black-holes-photography-m87.html |archivedate=24 January 2024 |accessdate=25 January 2024 }}</ref> whose mass is billions of times that of the Earth's Sun; estimates had ranged from {{val|3.5|0.8|e=9}}&nbsp;{{solar mass|link=yes}}<ref name=jwalsh/> to {{val|6.6|0.4|e=9}}&nbsp;{{solar mass|link=y}},<ref name="jwalsh"/> surpassed by {{val|7.22|0.34|0.40|e=9}}&nbsp;{{solar mass|link=y}} in 2016.<ref name="oldham2016"/> In April 2019, the [[Event Horizon Telescope]] collaboration released measurements of the black hole's mass as {{nowrap|(6.5 ± 0.2<sub>stat</sub> ± 0.7<sub>sys</sub>) × {{10^|9}} }} {{solar mass|link=y}}.<ref name="EHT4"/> This is one of the [[List of most massive black holes|highest known masses]] for such an object. A rotating disk of ionized gas surrounds the black hole, and is roughly perpendicular to the relativistic jet. The disk rotates at velocities of up to roughly {{convert|1,000|km/s|mph|abbr=unit}}<ref name=apj489/> and spans a maximum diameter of {{Convert|25,000|AU|e12km e12mi|abbr=unit}}.<ref name=al37_3_154/> By comparison, [[Pluto]] averages {{Convert|39|AU|e9km e9mi|abbr=unit}} from the Sun. Gas [[Bondi accretion|accretes]] onto the black hole at an estimated rate of one solar mass every ten years (about 90&nbsp;[[Earth mass]]es per day).<ref name=apj582_1/> The [[Schwarzschild radius]] of the black hole is {{convert|120|AU|e9km e9mi|abbr=in}}.<ref name=Akiyama2015/> The diameter of the ring of emission, as seen from Earth, is 42 μas ([[minute of arc|microarcsecond]]). By comparison, the diameter of the core of M87 is 45" (as, arcsecond), and the size of M87 is 7.2' x 6.8' (am, arcminute).

A 2010 paper suggested that the black hole may be displaced from the galactic center by about {{Convert|7|pc|ly|abbr=off|spell=in|lk=on}}.<ref name=apjl717_1_L6/> This was claimed to be in the opposite direction of the known jet, indicating acceleration of the black hole by it. Another suggestion was that the offset occurred during the merger of two supermassive black holes.<ref name=apjl717_1_L6/><ref name=sciencenews177_3_9/> However, a 2011 study did not find any statistically significant displacement,<ref name=gebhardt2011/> and a 2018 study of high-resolution images of M87 concluded that the apparent spatial offset was caused by temporal variations in the jet's brightness rather than a physical displacement of the black hole from the galaxy's center.<ref>{{cite journal |last1=López-Navas |first1=E. |last2=Prieto |first2=M.A. |year=2018 |title=The photocentre-AGN displacement: Is M87 actually harbouring a displaced supermassive black hole? |journal=Monthly Notices of the Royal Astronomical Society |volume=480 |issue=3 |page=4099 |doi=10.1093/mnras/sty2148 |doi-access=free |bibcode=2018MNRAS.480.4099L |arxiv=1808.04123 |s2cid=118872175 }}</ref>

This black hole is the first to be imaged. Data to produce the image were taken in April&nbsp;2017, the image was produced during 2018 and was published on 10&nbsp;April&nbsp;2019.<ref name=EHT2019/><ref name="NYT-20190410a"/><ref name="NASA-20190410"/> The image shows the [[Black hole#Observational evidence|shadow]] of the black hole,<ref>{{cite journal |last1=Falcke |first1=Heino |last2=Melia |first2=Fulvio |last3=Agol |first3=Eric |date=2000-01-01 |title=Viewing the shadow of the black hole at the galactic center |journal=The Astrophysical Journal |volume=528 |issue=1 |pages=L13–L16 |doi=10.1086/312423 |pmid=10587484|arxiv=astro-ph/9912263 |bibcode=2000ApJ...528L..13F |s2cid=119433133 |url=https://iopscience.iop.org/article/10.1086/312423}}</ref> surrounded by an asymmetric emission ring with a diameter of {{convert|690|AU|e9km e9mi|abbr=unit}}. The shadow radius is 2.6&nbsp;times that of the black hole's Schwarzschild radius. The asymmetry in the brightness of the ring is due to [[relativistic beaming]], whereby material moving towards the observer at relativistic velocities appears brighter. The visible material around the black hole rotates mostly clockwise with respect to the observer, which due to the direction of the axis of rotation causes the bottom part of the emission region to have a component of velocity toward the observer.<ref name="APJL-20190410a"/> The rotation parameter was estimated at <math>a=0.9 \pm 0.1</math>, corresponding to a rotation speed {{nobr| ≈ 0.4 [[speed of light|{{mvar|c}}]].}}<ref name=OAM_MNRASL2019/>
This is consistent with the value of <math>a=1.00 \pm 0.15</math>
obtained with the outflow method. <ref>{{cite journal |author1=Daly, R. A. |date= Nov 2019 |title=Black Hole Spin and Accretion Disk Magnetic Field Strength Estimates for More Than 750 Active Galactic Nuclei and Multiple Galactic Black Holes |journal=The Astrophysical Journal |volume=886 |issue=1 |pages=37  |doi=10.3847/1538-4357/ab35e6|doi-access=free |arxiv=1905.11319 }}</ref>

{{clear}}[[File:Telescopes Unite in Unprecedented Observations of Famous Black Hole M87.jpg|thumb|center|800px|Composite image showing how the M87 system looked, across the entire electromagnetic spectrum, during the Event Horizon Telescope's April&nbsp;2017 campaign to take the first image of a black hole. Requiring 19&nbsp;different facilities on the Earth and in space, this image reveals the enormous scales spanned by the black hole and its forward-pointing jet. It shows the image of the larger-scale jet taken by [[Atacama Large Millimeter Array|ALMA]] (upper left), on the same scale as the visible image by the Hubble Space Telescope (center) and the X-ray image by Chandra (upper right).<ref>{{cite press release |title=Telescopes unite in unprecedented observations of famous black hole |publisher=[[Atacama Large Millimeter Array]] |url=https://www.almaobservatory.org/en/audiences/telescopes-unite-in-unprecedented-observations-of-famous-black-hole/ |access-date=15 April 2021}}</ref>]]

After the black hole had been imaged, it was named '''Pōwehi''', a [[Hawaiian language|Hawaiian]] word meaning "the adorned fathomless dark creation", taken from the ancient creation chant [[Kumulipo]].<ref>{{cite news |last=Mele|first=Christopher |date=13 April 2019 |title=That first black hole seen in an image is now called Pōwehi, at least in Hawaii |newspaper=[[The New York Times]] |url=https://www.nytimes.com/2019/04/13/science/powehi-black-hole.html |access-date=March 20, 2021}}</ref>

On 24&nbsp;March&nbsp;2021, the Event Horizon Telescope collaboration revealed an unprecedented unique view of the M87 black hole shadow: how it looks in polarized light.<ref>{{cite journal |author1=Akiyama, Kazunori |collaboration=Event Horizon Telescope Collaboration |year=2021 |title=First M87 Event Horizon Telescope results. VII. Polarization of the ring |journal=The Astrophysical Journal |volume=910 |issue=1 |pages=L12|doi=10.3847/2041-8213/abe71d |arxiv=2105.01169 |bibcode=2021ApJ...910L..12E |s2cid=233851995 |doi-access=free }}</ref> Polarization is a powerful tool which allows astronomers to probe physics behind the image in more detail. Light polarization informs us about the strength and orientation of magnetic fields in the ring of light around the black hole shadow.<ref>{{cite journal |last1=Akiyama|first1=Kazunori |collaboration=Event Horizon Telescope Collaboration |year=2021 |title=First M87 Event Horizon Telescope results. VIII. Magnetic field structure near the event horizon |journal=The Astrophysical Journal |volume=910 |issue=1 |page=L13 |doi=10.3847/2041-8213/abe4de |arxiv=2105.01173 |bibcode=2021ApJ...910L..13E |s2cid=233715131 |doi-access=free }}</ref> Knowing those is essential to understand how M87's supermassive black hole is launching jets of magnetized plasma, which expand at relativistic speeds beyond the M87 galaxy.

[[File:EHT-PRIMO-refinement.jpg|thumb|right|500px|Sharpening of the original EHT imaging of the M87 black hole, using the PRIMO technique for interferometric modeling. The rightmost image adds back in some fuzzing to account for the limited resolving power of the underlying observations.]]On 14&nbsp;April&nbsp;2021, astronomers further reported that the M87 black hole and its surroundings were studied during Event Horizon Telescope 2017 observing run also by many multi-wavelength observatories from around the world.{{clarification needed|date=January 2023}}<ref name="NASA-20210414">{{cite press release |last1=Edmonds |first1=Peter |last2=Cofield |first2=Calla |date=14 April 2021 |title=Telescopes unite in unprecedented observations of famous black hole |publisher=[[NASA]] |quote=Some of the world's most powerful telescopes simultaneously observed the supermassive black hole in galaxy M87, the first black hole to be directly imaged. |url=https://www.jpl.nasa.gov/news/telescopes-unite-in-unprecedented-observations-of-famous-black-hole |access-date=14 April 2021 }}</ref>

In April 2023, a team developed a new principal-component interferometric modeling (PRIMO) technique to produce sharper image reconstructions from EHT data. They applied this to the original EHT observations of the M87 black hole, yielding a crisper final image and allowing closer testing of the alignment of observations to theory.<ref>{{Cite web |author1=Robert Lea |date=2023-04-13 |title=The 1st-ever photo of a supermassive black hole just got an AI 'makeover' and it looks absolutely amazing |url=https://www.space.com/first-ever-black-hole-image-ai-makeover |access-date=2023-10-19 |website=Space.com |language=en}}</ref><ref>{{Cite journal |last1=Medeiros |first1=Lia |last2=Psaltis |first2=Dimitrios |last3=Lauer |first3=Tod R. |last4=Özel |first4=Feryal |date=April 2023 |title=The Image of the M87 Black Hole Reconstructed with PRIMO |journal=The Astrophysical Journal Letters |language=en |volume=947 |issue=1 |pages=L7 |doi=10.3847/2041-8213/acc32d |issn=2041-8205 |doi-access=free |arxiv=2304.06079 |bibcode=2023ApJ...947L...7M }}</ref>

===Jet===
{{multiple image
| align             = right
| direction         = horizontal
| total_width       = 400
| image1            = M87 jet.jpg
| caption1          = The [[Astrophysical jet#Relativistic jet|jet of matter]] is ejected from M87 at nearly the [[speed of light]], and stretches {{cvt|1.5|kpc|kly|sigfig=1}} from the galactic core.
| alt1              = M87 jet extends up to 5,000 light-years from the core
| image2            = M87 Super-Volcano.jpg
| caption2          = In this X-ray ([[Chandra X-ray Observatory|Chandra]]) and radio ([[Very Large Array|VLA]]) composite image, hot matter (blue in X-ray) from the Virgo cluster falls toward the core of M87 and cools, where it is met by the relativistic jet (orange in radio), producing shock waves in the galaxy's interstellar medium.
| alt2              = In X-ray image, blue appearing hot matter from cluster falls to M87 center and cools, thus fading in brightness. Jet (appearing orange in radio) hinders this infall and lifts the falling matter up.
}}

The [[relativistic jet]] of matter emerging from the core extends at least {{convert|1.5|kpc|ly|abbr=off|sigfig=1}} from the nucleus and consists of matter ejected from a supermassive black hole. The jet is highly [[Collimated beam|collimated]], appearing constrained to an angle of 60° within {{convert|0.8|pc|abbr=in}} of the core, to about 16° at {{convert|2|pc|abbr=off|spell=in}}, and to 6–7° at {{convert|12|pc|abbr=off|spell=in}}.<ref name=Doeleman2012/> Its base has the diameter of {{nobr| 5.5 ± 0.4 [[Schwarzschild radius|Schwarzschild radii]],}} and is probably powered by a [[Retrograde and prograde motion|prograde]] accretion disk around the spinning supermassive black hole.<ref name=Doeleman2012/> The German-American astronomer [[Walter Baade]] found that light from the jet was [[Linear polarization|plane polarized]], which suggests that the energy is generated by the acceleration of electrons moving at [[Special relativity|relativistic velocities]] in a [[magnetic field]]. The total energy of these electrons is estimated at {{nobr|5.1 × {{10^|56}}}} [[erg]]s<ref name=observatory76/> ({{nobr|5.1 × {{10^|49}} [[joule]]s}} or {{nobr|3.2 × {{10^|68}} [[Electronvolt|eV]]}}). This is roughly {{10^|13}}&nbsp;times the energy produced in the entire Milky Way in one second, which is estimated at {{nobr| 5 × {{10^|36}} joules.}}<ref name=vdb1999/> The jet is surrounded by a lower-velocity non-relativistic component. There is evidence of a counter jet, but it remains unseen from the Earth due to [[relativistic beaming]].<ref name=apj668_1_L27/><ref name=nature355_804/> The jet is [[precession|precessing]], causing the outflow to form a helical pattern out to {{Convert|1.6|pc|abbr=off}}.<ref name=al37_3_154/> Lobes of expelled matter extend out to {{Convert|80|kpc|ly|abbr=off}}.<ref name=klein1997/>

In pictures taken by the Hubble Space Telescope in 1999, the motion of M87's jet was measured at four to six times the speed of light. This phenomenon, called [[superluminal motion]], is an illusion caused by the relativistic velocity of the jet. The time interval between any two light pulses emitted by the jet is, as registered by the observer, less than the actual interval due to the relativistic speed of the jet moving in the direction of the observer. This results in perceived [[faster-than-light]] speeds, though the jet itself has a velocity of only 80–85% the speed of light. Detection of such motion is used to support the theory that [[quasar]]s, [[BL Lacertae object]]s and [[radio galaxies]] may all be the same phenomenon, known as [[active galactic nucleus|active galaxies]], viewed from different perspectives.<ref name=apj520_2/><ref name=hubble990106/> It is proposed that the nucleus of M87 is a BL&nbsp;Lacertae object (of lower luminosity than its surrounds) seen from a relatively large angle. Flux variations, characteristic of the BL&nbsp;Lacertae objects, have been observed in M87.<ref name=arxiv_1997/><ref name=M87_blazar/>
[[File:Close-Up Look at a Jet Near a Black Hole.jpg|thumb|left| Radio wavelength image of M87 showing strong radio emission from the core|alt=M87 black hole is a strong source of radio waves]]

Observations indicate that the rate at which material is ejected from the supermassive black hole is variable. These variations produce pressure waves in the hot gas surrounding M87. The [[Chandra X-ray Observatory]] has detected loops and rings in the gas. Their distribution suggests that minor eruptions occur every few&nbsp;million years. One of the rings, caused by a major eruption, is a shock wave {{convert|26|kpc|ly|abbr=off}} in diameter around the black hole. Other features observed include narrow X-ray-emitting filaments up to {{convert|31|kpc|ly|abbr=off}} long, and a large cavity in the hot gas caused by a major eruption 70&nbsp;million years ago. The regular eruptions prevent a huge reservoir of gas from cooling and forming stars, implying that M87's evolution may have been seriously affected, preventing it from becoming a large spiral galaxy.

M87 is a very strong source of [[gamma ray]]s, the most energetic rays of the electromagnetic spectrum. Gamma rays emitted by M87 have been observed since the late 1990s. In 2006, using the [[High Energy Stereoscopic System]] Cherenkov telescopes, scientists measured the variations of the gamma ray flux coming from M87, and found that the flux changes over a matter of days. This short period indicates that the most likely source of the gamma rays is a supermassive black hole.<ref name=cain061027/> In general, the smaller the diameter of the emission source, the faster the variation in flux.<ref name=cain061027/><ref name=Peterson2001/>

{{multiple image
| align = right
| direction = horizontal
| total_width = 400
| image1 = PIA23122-M87-SMBH-SpitzerST-Closeup-20190424.jpg
| caption1 = M87 in infrared showing shocks produced by the jets
| image2 = Hubble follows spiral flow of black-hole-powered jet.jpg
| caption2 = Spiral flow of the black hole-powered jet<ref name=hfsf/>
| alt2 = Images showing helical flow of matter in M87 jet
}}

A knot of matter in the jet (designated HST-1), about {{Convert|65|pc|abbr=off}} from the core, has been tracked by the Hubble Space Telescope and the Chandra X-ray Observatory. By 2006, the X-ray intensity of this knot had increased by a factor of 50 over a four-year period,<ref name=apj640_1/> while the X-ray emission has since been decaying in a variable manner.<ref name=baas41/>

The interaction of relativistic jets of plasma emanating from the core with the surrounding medium gives rise to [[radio lobe]]s in active galaxies. The lobes occur in pairs and are often symmetrical.<ref name=schneider2006/> The two radio lobes of M87 together span about 80&nbsp;kiloparsecs; the inner parts, extending up to 2&nbsp;kiloparsecs, emit strongly at radio wavelengths. Two flows of material emerge from this region, one aligned with the jet itself and the other in the opposite direction. The flows are asymmetrical and deformed, implying that they encounter a dense intra-cluster medium. At greater distances, both flows diffuse into two lobes. The lobes are surrounded by a fainter halo of radio-emitting gas.<ref name=owen2000/><ref name=coolcosmos1/>

===Interstellar medium===
The space between the stars in M87 is filled with a diffuse interstellar medium of gas that has been chemically enriched by the elements ejected from stars as they passed beyond their [[main sequence]] lifetime. Carbon and nitrogen are continuously supplied by stars of intermediate mass as they pass through the [[asymptotic giant branch]].<ref name=aaa459_2/><ref name=Werner2008/> The heavier elements from oxygen to iron are produced largely by supernova explosions within the galaxy. Of the heavy elements, about 60% were produced by core-collapse supernovae, while the remainder came from [[type Ia supernova]]e.<ref name=aaa459_2/>

The distribution of oxygen is roughly uniform throughout, at about half of the [[Sun#Composition|solar value]] (i.e., oxygen abundance in the Sun), while iron distribution peaks near the center where it approaches the solar iron value.<ref name=Werner2008/><ref name=Finoguenov2002/> Since oxygen is produced mainly by core-collapse supernovae, which occur during the early stages of galaxies, and mostly in outer star-forming regions,<ref name=aaa459_2/><ref name=Werner2008/><ref name=Finoguenov2002/> the distribution of these elements suggests an early enrichment of the interstellar medium from core-collapse supernovae and a continuous contribution from type&nbsp;Ia supernovae throughout the history of M87.<ref name=aaa459_2/> The contribution of elements from these sources was much lower than in the Milky Way.<ref name=aaa459_2/>
{| class="wikitable" style="float: right; text-align: center; margin-left: 0.5em;"
|+ Selected elemental abundances in the M87 core<ref name=aaa459_2/>
|- style="background-color: #eeeeee;"
| '''Element'''
| '''Abundance'''<br />(solar values)
|-
| C || 0.63 ± 0.16
|-
| N || 1.64 ± 0.24
|-
| O || 0.58 ± 0.03
|-
| Ne || 1.41 ± 0.12
|-
| Mg || 0.67 ± 0.05
|-
| Fe || 0.95 ± 0.03
|}
Examination of M87 at far [[infrared]] wavelengths shows an excess emission at wavelengths longer than 25&nbsp;μm. Normally, this may be an indication of [[Thermal radiation|thermal emission]] by warm dust.<ref name=apj655_2_781/> In the case of M87, the emission can be fully explained by [[synchrotron radiation]] from the jet; within the galaxy, silicate grains are expected to survive for no more than 46&nbsp;million years because of the X-ray emission from the core.<ref name=aaa518_1/> This dust may be destroyed by the hostile environment or expelled from the galaxy.<ref name=aaa518_1III/> The combined mass of dust in M87 is no more than 70,000&nbsp;times the mass of the Sun.<ref name=aaa518_1/> By comparison, the Milky Way's dust equals about a hundred&nbsp;million ({{10^|8}}) solar masses.<ref name=jones2004/>

Although M87 is an elliptical galaxy and therefore lacks the dust lanes of a spiral galaxy, optical filaments have been observed in it, which arise from gas falling towards the core. Emission probably comes from shock-induced excitation as the falling gas streams encounter X-rays from the core region.<ref name=Ford19792/> These filaments have an estimated mass of about 10,000&nbsp;{{solar mass|link=y}}.<ref name=aj86/><ref name=Ford19792/> Surrounding the galaxy is an extended corona with hot, low-density gas.<ref name=aj115_5/>

===Globular clusters===
M87 has an abnormally large population of globular clusters. A 2006 survey out to an angular distance of 25[[arcminute|′]]<!--again, what is this in parsecs at distance of M87?--> from the core estimates that there are {{nobr| 12,000 ± 800 globular }} clusters in orbit around M87,<ref name=mnras373_2/> compared with 150–200 in and around the Milky Way. The clusters are similar in size distribution to those of the Milky Way, most having an effective radius of 1 to 6&nbsp;parsecs. The size of the M87 clusters gradually increases with distance from the galactic center.<ref name=apj705_1_237/> Within a {{convert|4|kpc|ly|abbr=off|adj=on|spell=in}} radius of the core, the cluster [[metallicity]]—the abundance of elements other than hydrogen and helium—is about half the abundance in the Sun. Outside this radius, metallicity steadily declines as the cluster distance from the core increases.<ref name=aj115_5/> Clusters with low metallicity are somewhat larger than metal-rich clusters.<ref name=apj705_1_237/> In 2014, [[HVGC-1]], the first hypervelocity globular cluster, was discovered escaping from M87 at 2,300&nbsp;km/s. The escape of the cluster with such a high velocity was speculated to have been the result of a close encounter with, and subsequent gravitational kick from, a supermassive black hole binary.<ref name=2014arXiv1402.6319C/>

Almost a hundred ultra-compact [[Dwarf galaxy|dwarfs]] have been identified in M87. They resemble globular clusters but have a diameter of {{Convert|10|pc|abbr=off|spell=in}} or more, much larger than the {{convert|3|pc|abbr=off|adj=on|spell=in}} maximum of globular clusters. It is unclear whether they are dwarf galaxies captured by M87 or a new class of massive globular cluster.<ref name="Zhang 2015"/>

==Environment==
{{Main|Virgo Cluster}}
[[File:ESO-M87.jpg|thumb|Photograph of the Virgo Cluster ([[European Southern Observatory]] 2009). M87 is visible in the lower left, the upper half of the image is taken up by [[Markarian's Chain]].
The dark spots mark the locations of bright foreground stars that were removed from the image.|alt=Visible wavelength image of Virgo cluster with M87 near lower left]]

M87 is near (or at) the center of the Virgo Cluster,<ref name=mnras377_1/> a closely compacted structure of about 2,000&nbsp;galaxies.<ref name=apjss153_1_223/> This forms the core of the larger [[Virgo Supercluster]], of which the [[Local Group]] (including the Milky Way) is an outlying member.<ref name=aaa502_3/> It is organized into at least three distinct subsystems associated with the three large galaxies—M87, [[Messier 49|M49]] and [[Messier 86|M86]]—with the core subgroup including M87 (''Virgo&nbsp;A'') and M49 (''Virgo&nbsp;B'').<ref name="BinggeliNED"/> There is a preponderance of elliptical and [[S0 galaxy|S0&nbsp;galaxies]] around M87.<ref name=aj94/> A chain of elliptical galaxies roughly aligns with the jet.<ref name=aj94/> In terms of mass, M87 is likely to be the largest, and coupled with centrality appears to be moving very little relative to the cluster as a whole.<ref name=aaa502_3/> It is defined in one study as the cluster center. The cluster has a sparse gaseous medium that emits X-rays, lower in temperature toward the middle.<ref name=apj655_2_781/> The combined mass of the cluster is estimated to be 0.15 to {{nobr| 1.5 × {{10^|15}} {{solar mass|link=y}}.}}<ref name=apjss153_1_223/>

Measurements of the motion of those intracluster starburst ("planetary") nebulae between M87 and M86 suggest that the two galaxies are moving toward each other and that this may be their first encounter. M87 may have interacted with [[Messier 84|M84]], as evidenced by the truncation of M87's outer halo by [[Tidal force|tidal interactions]]. The truncated halo may also have been caused by contraction due to an unseen mass falling into M87 from the rest of the cluster, which may be the hypothesized [[dark matter]]. A third possibility is that the halo's formation was truncated by early feedback from the active galactic nucleus.<ref name=aaa502_3/>

==See also==
* [[List of Messier objects]]

==Notes==
{{notelist}}

==References==
{{reflist|22em|refs=

<ref name=aaa493_1>{{cite journal |author1=Lambert, S.B. |author2=Gontier, A.-M. |date=January 2009 |title=On radio source selection to define a stable celestial frame |journal=[[Astronomy and Astrophysics]] |volume=493 |issue=1 |pages=317–323 |bibcode=2009A&A...493..317L |doi=10.1051/0004-6361:200810582 |doi-access=free }} See the [http://simbad.u-strasbg.fr/simbad/sim-ref?bibcode=2009A%26A...493..317L&simbo=on tables] in particular.</ref>

<ref name=ned>{{cite web |url=https://ned.ipac.caltech.edu/byname?objname=NGC%204486 |title=Results for NGC 4486 |website=NASA/IPAC Extragalactic Database |publisher=California Institute of Technology |access-date=8 April 2019}}
<!-- from [https://ned.ipac.caltech.edu/ ned.ipac.caltech.edu] enter "NGC 4486" into search box.-->
</ref>

<ref name=2011MNRAS>{{cite journal |last1=Cappellari |first1=Michele |display-authors=etal |title=The ATLAS<sup>3D</sup> project – I. A volume-limited sample of 260 nearby early-type galaxies: science goals and selection criteria |journal=Monthly Notices of the Royal Astronomical Society |date=11 May 2011 |volume=413 |issue=2 |pages=813–836 |bibcode=2011MNRAS.413..813C |doi=10.1111/j.1365-2966.2010.18174.x|doi-access=free |arxiv=1012.1551 |s2cid=15391206 }}</ref>
<!--
<ref name=apjss164_2_334>{{cite journal |author=Ferrarese, L. |display-authors=etal |date=June 2006|title=The ACS Virgo Cluster Survey. VI. Isophotal Analysis and the Structure of Early-Type Galaxies |journal=[[The Astrophysical Journal Supplement Series]] |volume=164 |issue=2 |pages=334–434 |doi=10.1086/501350 |bibcode=2006ApJS..164..334F |arxiv=astro-ph/0602297|s2cid=18618068 }}</ref> -->

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<ref name=apj643_1>{{cite journal |author=Wu, X. |author2=Tremaine, S. |year=2006 |title=Deriving the Mass Distribution of M87 from Globular Clusters |journal=The Astrophysical Journal |volume=643 |issue=1 |pages=210–221 |arxiv=astro-ph/0508463 |bibcode=2006ApJ...643..210W |doi=10.1086/501515|s2cid=9263634 }}</ref>

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<ref name=apj520_2>{{cite journal |author=Biretta, J.A. |author2=Sparks, W.B. |author3=Macchetto, F. |title=Hubble Space Telescope Observations of Superluminal Motion in the M87 Jet |journal=The Astrophysical Journal |volume=520 |issue=2 |pages=621–626 |date=August 1999 |bibcode=1999ApJ...520..621B |doi=10.1086/307499|doi-access=free }}</ref>

<ref name=hubble990106>{{cite web |url=http://www.stsci.edu/ftp/science/m87/press.txt |title=Hubble detects faster-than-light motion in Galaxy M87 |author=Biretta, J. |publisher=Space Telescope Science Institute |location=Baltimore, Maryland |date=6 January 1999 |access-date=21 March 2018}}</ref>

<ref name=cain061027>{{cite news |author=Wirsing, B. |date=26 October 2006 |title=Discovery of Gamma Rays from the Edge of a Black Hole |publisher=Max Planck Society |url=http://www.mpg.de/english/illustrationsDocumentation/documentation/pressReleases/2006/pressRelease20061025/ |access-date=3 December 2010 |url-status=live |archive-url=https://web.archive.org/web/20110103073232/http://www.mpg.de/english/illustrationsDocumentation/documentation/pressReleases/2006/pressRelease20061025/ |archive-date=3 January 2011 }}</ref>

<ref name=aaa502_3>{{cite journal |author=Doherty, M. |author2=Arnaboldi, M. |author3=Das, P. |author4=Gerhard, O. |author5=Aguerri, J.A.L. |author6=Ciardullo, R. |author7=Feldmeier, J.J. |author8=Freeman, K.C. |author9=Jacoby, G.H. |author10=Murante, G. |date=August 2009 |title=The edge of the M87 halo and the kinematics of the diffuse light in the Virgo cluster core |journal=Astronomy and Astrophysics |volume=502 |issue=3 |pages=771–786 |arxiv=0905.1958|bibcode=2009A&A...502..771D|doi=10.1051/0004-6361/200811532|s2cid=17110964 }}</ref>

<ref name=klotz090608>{{cite news |author=Klotz, I. |date=8 June 2009 |title=Galaxy's outer halo lopped off |website=Discovery |series=News |url=http://dsc.discovery.com/news/2009/06/08/galaxy-messier-star.html |access-date=25 April 2010 |archive-url=https://web.archive.org/web/20090823162018/http://dsc.discovery.com/news/2009/06/08/galaxy-messier-star.html |archive-date=23 August 2009 }}</ref>

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<ref name=apj56>{{cite journal |author=Hubble, E. P. |date=October 1922 |title=A general study of diffuse galactic nebulae |journal=[[The Astrophysical Journal]] |volume=56 |pages=162–199 |bibcode=1922ApJ....56..162H |doi=10.1086/142698|doi-access=free }}</ref>

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<ref name=pasp35_207>{{cite journal |author=Hubble, E. |date=October 1923 |title=Messier 87 and Belanowsky's Nova |journal=[[Publications of the Astronomical Society of the Pacific]] |volume=35 |issue=207 |pages=261–263 |bibcode=1923PASP...35..261H |doi=10.1086/123332|doi-access=free }}</ref>

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<ref name=jones_lambourne04>{{cite book |author=Jones, M. H. |author2=Lambourne, R. J. |date=2004 |title=An introduction to galaxies and cosmology |publisher=Cambridge University Press|page=69 |isbn=978-0-521-54623-2}}</ref>

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<ref name=apj209>{{cite journal |author=Oemler, A. Jr. |date=November 1976 |title=The structure of elliptical and cD galaxies |journal=The Astrophysical Journal |volume=209 |pages=693–709 |bibcode=1976ApJ...209..693O |doi=10.1086/154769|doi-access=free }}</ref>

<ref name=whitmore89>{{cite conference |first=B. C. |last=Whitmore |title=Effect of the Cluster Environment on Galaxies |page=151 |book-title=Clusters of galaxies: proceedings of the Clusters of Galaxies Meeting |volume=4 |series=Space Telescope Science Institute symposium series |location=Baltimore |date= 15–17 May 1989 |editor=William R. Oegerle |editor2=Michael J. Fitchett |editor3=Laura Danly |publisher=Cambridge University Press |isbn=0-521-38462-1}}</ref>

<ref name=luginbuhl_skiff98>{{cite book |author=Luginbuhl, C. B. |author2=Skiff, B. A. |date=1998 |title=Observing Handbook and Catalogue of Deep-Sky Objects |edition=2nd |location=Cambridge, United Kingdom|publisher=Cambridge University Press |page=266 |isbn=978-0-521-62556-2}}.
The dimensions of 7′.2 x 6′.8 refer to the size of the halo as visible in amateur astronomy. "The galaxy is up to 4′ diameter in 25 cm. The 45″ core is of very high surface brightness."</ref>

<ref name=clark90>{{cite book |author=Clark, R. N. |date=1990 |title=Visual astronomy of the deep sky |publisher=Cambridge University Press |page=153 |isbn=978-0-521-36155-2}}</ref>

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<ref name=bradt68>{{cite journal |author=Bradt, H. |author2=Naranan, S. |author3=Rappaport, S. |author4=Spada, G. |date=June 1968 |title=Celestial Positions of X-ray Sources in Sagittarius |journal=The Astrophysical Journal |volume=152 |issue=6 |pages=1005–1013 |bibcode=1968ApJ...152.1005B |doi=10.1086/149613|s2cid=121431446 |doi-access=free }}</ref>

<ref name=apj262>{{cite journal |author=Lea, S. M. |author2=Mushotzky, R. |author3=Holt, S. S. |date=November 1982 |title=Einstein Observatory solid state spectrometer observations of M87 and the Virgo cluster |journal=Astrophysical Journal, Part 1 |volume=262 |pages=24–32 |bibcode=1982ApJ...262...24L |doi=10.1086/160392|hdl=2060/19820026438 |s2cid=120960432 |hdl-access=free }}</ref>

<ref name=mnras170>{{cite journal |author=Turland, B. D. |date=February 1975 |title=Observations of M87 at 5 GHz with the 5-km telescope |journal=[[Monthly Notices of the Royal Astronomical Society]] |volume=170 |issue=2 | pages=281–294 |bibcode=1975MNRAS.170..281T |doi=10.1093/mnras/170.2.281 |doi-access=free }}</ref>

<ref name=apj486>{{cite journal |author=Cohen, J. G. |author2=Ryzhov, A. |date=September 1997 |title=The Dynamics of the M87 Globular Cluster System |journal=The Astrophysical Journal |volume=486 |issue=1 |pages=230–241 |arxiv = astro-ph/9704051 |bibcode=1997ApJ...486..230C |doi=10.1086/304518|s2cid=13517745 }}</ref>

<ref name=janowiecki10>{{cite journal |author=Janowiecki, S. |author2=Mithos, J. C. |author3=Harding, P. |author4=Feldmeier, J. |author5=Rudick, C. |author6=Morrison, H. |date=June 2010 |title=Diffuse Tidal Structures in the Halos of Virgo Ellipticals |journal=The Astrophysical Journal |volume=715 |issue=2 |pages=972–985 |arxiv=1004.1473 |bibcode=2010ApJ...715..972J |doi=10.1088/0004-637X/715/2/972|s2cid=119196248 }}</ref>

<ref name=apj640_1>{{cite journal |author1=Harris, D.E. |author2=Cheung, C.C. |author3=Biretta, J.A. |author4=Sparks, W.B. |author5=Junor, W. |author6=Perlman, E.S. |author7=Wilson, A.S. |year=2006 |title=The Outburst of HST-1 in the M87 Jet |journal=The Astrophysical Journal |volume=640 |issue=1 |pages=211–218 |arxiv = astro-ph/0511755 |bibcode=2006ApJ...640..211H |doi=10.1086/500081| s2cid=17268539 }}</ref>

<ref name=baas41>{{cite journal |author1=Harris, D. E. |author2=Cheung, C. C. |author3=Stawarz, L. |date=July 2009 |title=Variability time scales in the M87 Jet: Signatures of E squared losses, discovery of a quasi-period in HST-1, and the site of TeV flaring |journal=The Astrophysical Journal |volume=699 |issue=1 |pages=305–314 |arxiv=0904.3925 |bibcode=2009ApJ...699..305H |doi=10.1088/0004-637X/699/1/305|s2cid=14475336 }}</ref>

<ref name=mnras377_1>{{cite journal |author=Chakrabarty, D. |year=2007 |title=Mass modelling with minimum kinematic information |journal=Monthly Notices of the Royal Astronomical Society |volume=377 |issue=1 |pages=30–40 |arxiv=astro-ph/0702065 |bibcode=2007MNRAS.377...30C |doi=10.1111/j.1365-2966.2007.11583.x|doi-access=free |s2cid=16263041 }}</ref>

<ref name=apj106_6>{{cite journal |author=Merritt, D. |author-link=David Merritt |author2= Tremblay, B. |date=December 1993 |title=The distribution of dark matter in the halo of M87 |journal=The Astronomical Journal |volume=106 |issue=6 |pages=2229–2242 |doi=10.1086/116796 |bibcode=1993AJ....106.2229M |doi-access=free }}</ref>

<ref name=aaa459_2>{{cite journal |author=Werner, N. |author2=Böhringer, H. |author3=Kaastra, J. S. |author4=de Plaa, J. |author5=Simionescu, A. |author6=Vink, J. |date=November 2006 |title=XMM-Newton high-resolution spectroscopy reveals the chemical evolution of M87 |journal=Astronomy and Astrophysics |volume=459 |issue=2 |pages=353–360 |doi=10.1051/0004-6361:20065678 |bibcode=2006A&A...459..353W |arxiv=astro-ph/0608177 |s2cid=18790420 }}</ref>

<ref name=Werner2008>{{cite journal |author=Werner, N. |author2=Durret, F. |author3=Ohashi, T. |author4=Schindler, S. |author5=Wiersma, R.P.C. |date=February 2008 |title=Observations of metals in the intra-cluster medium |journal=[[Space Science Reviews]] |volume=134 |issue=1–4 |pages=337–362 |doi=10.1007/s11214-008-9320-9 |bibcode=2008SSRv..134..337W |arxiv=0801.1052|s2cid=15906129 }}</ref>

<ref name=Finoguenov2002>{{cite journal |author=Finoguenov, A. |author2=Matsushita, K. |author3=Böhringer, H. |author4=Ikebe, Y. |author5=Arnaud, M. |date=January 2002|title=X-ray evidence for spectroscopic diversity of type Ia supernovae: XMM observation of the elemental abundance pattern in M87 | journal=Astronomy and Astrophysics |volume=381 |number=1 |pages=21–31 |doi=10.1051/0004-6361:20011477 |bibcode=2002A&A...381...21F|arxiv=astro-ph/0110516|s2cid=119426359 }}</ref>

<ref name=aj115_5>{{cite journal |author=Harris, William E. |author2=Harris, Gretchen L. H. |author3=McLaughlin, Dean E. |date=May 1998 |title=M87, Globular Clusters, and Galactic Winds: Issues in Giant Galaxy Formation |journal=The Astronomical Journal |volume=115 |issue=5 |pages=1801–1822 |doi=10.1086/300322 |bibcode=1998AJ....115.1801H |arxiv=astro-ph/9801214 |s2cid=119490384 }} The authors give a [[metallicity]] of:
:<math>\begin{smallmatrix}\left[\frac{Fe}{H}\right]\ =\ -0.3\end{smallmatrix}</math>
within a 3-kiloparsec radius of the galactic core.</ref>

<ref name=mnras364>{{cite journal |author=Battaglia, G. |author2=Helmi, A. |author3=Morrison, H. |author4=Harding, P. |author5=Olszewski, E. W. |author6=Mateo, M. |author7=Freeman, K. C. |author8=Norris, J. |author9=Shectman, S. A. |date=December 2005|title=The radial velocity dispersion profile of the Galactic halo: Constraining the density profile of the dark halo of the Milky Way |journal=Monthly Notices of the Royal Astronomical Society |volume=364 |issue=2 |pages=433–442 |doi=10.1111/j.1365-2966.2005.09367.x |doi-access=free |bibcode=2005MNRAS.364..433B |arxiv=astro-ph/0506102 |s2cid=15562509 }}</ref>

<ref name=leverington00>{{cite book |author=Leverington, D. |date=2000 |title=New Cosmic Horizons: Space astronomy from the V2 to the Hubble Space Telescope |publisher=Cambridge University Press |page=343|isbn=978-0-521-65833-1}}</ref>

<ref name=apj489>{{cite journal |author=Macchetto, F. |author2=Marconi, A. |author3=Axon, D.J. |author3-link=David Axon |author4=Capetti, A. |author5=Sparks, W. |author6=Crane, P. |date=November 1997 |title=The Supermassive Black Hole of M87 and the Kinematics of Its Associated Gaseous Disk |journal=The Astrophysical Journal |volume=489 |issue=2 |pages=579–600 |doi=10.1086/304823 |bibcode=1997ApJ...489..579M |arxiv=astro-ph/9706252|s2cid=18948008 }}</ref>

<ref name=apj582_1>{{cite journal |author1=di Matteo, . |author2=Allen, S.W. |author3=Fabian, A.C. |author4=Wilson, A.S. |author5=Young, A.J. |year=2003| title=Accretion onto the supermassive black hole in M87 |journal=The Astrophysical Journal |volume=582 |issue=1 |pages=133–140 |doi=10.1086/344504 |bibcode=2003ApJ...582..133D |arxiv=astro-ph/0202238 |s2cid=16182340 }}</ref>

<ref name=jwalsh>{{cite journal |author=Walsh, J.L. |author2= Barth, A.J. |author3= Ho, L.C. |author4= Sarzi, M. |date=June 2013 |title=The M87 black hole mass from gas-dynamical models of Space Telescope Imaging Spectrograph observations |journal=The Astrophysical Journal |volume=770 |issue=2 |page=86 |doi=10.1088/0004-637X/770/2/86 |bibcode=2013ApJ...770...86W |arxiv=1304.7273|s2cid= 119193955 }}</ref>

<ref name="oldham2016">{{cite journal |author=Oldham, L.J. |author2=Auger, M.W. |date=March 2016 |title=Galaxy structure from multiple tracers – II. M87 from parsec to megaparsec scales |journal=Monthly Notices of the Royal Astronomical Society |volume=457 |issue=1 |pages=421–439 |doi=10.1093/mnras/stv2982|doi-access=free |arxiv=1601.01323 |bibcode=2016MNRAS.457..421O |s2cid=119166670 }}
</ref>

<ref name=sciencenews177_3_9>{{cite news |author1=Cowen, R. |date=9 June 2010 |title=Black hole shoved aside, along with 'central' dogma |magazine=Science News |volume=177 |issue=13 |page=9 |url=http://www.sciencenews.org/view/generic/id/59656/title/Black_hole_shoved_aside,_along_with_central_dogma |access-date=29 May 2010 |archive-url=https://web.archive.org/web/20100528183417/http://www.sciencenews.org/view/generic/id/59656/title/Black_hole_shoved_aside,_along_with_central_dogma |archive-date=28 May 2010 }}</ref>

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<ref name="apj700_2_1690">{{cite journal |author=Gebhardt, K. |author2=Thomas, J. |year=2009 |title=The black hole mass, stellar mass-to-light ratio, and dark halo in M87 |journal=The Astrophysical Journal |volume=700 |issue=2 |pages=1690–1701 |doi=10.1088/0004-637X/700/2/1690 |bibcode=2009ApJ...700.1690G |arxiv=0906.1492 |s2cid=15481963 }}</ref>

<ref name=klein1997>{{cite conference |last=Klein |first=Uli |date=15–19 September 1997 |title=The large-scale structure of Virgo&nbsp;A |book-title=The Radio Galaxy Messier&nbsp;87 |series=Lecture Notes in Physics |volume=530 |pages=56–65 |location=Ringberg Castle, Tegernsee, Germany |editor1=Röser, Hermann-Josef |editor2=Meisenheimer, Klaus |publisher=Springer |doi=10.1007/BFb0106418 |bibcode=1999LNP...530...56K |isbn=978-3-540-66209-9 }}</ref>

<ref name=astromall>{{cite web |url=http://astronomy-mall.com/Adventures.In.Deep.Space/m87jet.htm| title=Visual observations of the M87 jet |website=Adventures in Deep Space |publisher=Astronomy-Mall |access-date=7 December 2010 | url-status=live | archive-url=https://web.archive.org/web/20110707180911/http://astronomy-mall.com/Adventures.In.Deep.Space/m87jet.htm | archive-date=7 July 2011 }}</ref>

<ref name=apj705_1_237>{{cite journal |author=Madrid, J.P. |author2=Harris, W.E. |author3=Blakeslee, J.P. |author4=Gómez, M. |year=2009 |title=Structural Parameters of the Messier 87 Globular Clusters |journal=The Astrophysical Journal |volume=705 |issue=1 |pages=237–244 |doi=10.1088/0004-637X/705/1/237 |bibcode=2009ApJ...705..237M |arxiv=0909.0272 |s2cid=15019649 }} See Fig. 6. for a plot of the effective cluster radius versus galactocentric distance.</ref>

<ref name=aaa518_1>{{cite journal |author1=Baes, M. |display-authors=etal |date=July 2010 | title=The Herschel Virgo Cluster Survey. VI. The far-infrared view of M87 |journal=Astronomy and Astrophysics |volume=518 |pages=L53 |doi=10.1051/0004-6361/201014555 |bibcode=2010A&A...518L..53B |arxiv =1005.3059|s2cid=27004145 }}</ref>

<ref name=aaa524_1>{{cite journal |author=Bird, S. |author2=Harris, W.E. |author3=Blakeslee, J. P. |author4=Flynn, C. |date=December 2010 |title=The inner halo of M87: A first direct view of the red-giant population |journal=Astronomy and Astrophysics |volume=524 |pages=A71 |doi=10.1051/0004-6361/201014876 |bibcode=2010A&A...524A..71B |arxiv=1009.3202|s2cid=119281578 }}</ref>

<ref name=apjss153_1_223>{{cite journal |author=Côté, P. |display-authors=etal |date=July 2004|title=The ACS Virgo Cluster Survey. I. Introduction to the survey |journal=[[The Astrophysical Journal Supplement Series]] |volume=153 |issue=1 |pages=223–242 |doi=10.1086/421490 |bibcode=2004ApJS..153..223C |arxiv=astro-ph/0404138 |s2cid=18021414 }}</ref>

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<ref name=apj124_416>{{cite journal |author=Burbidge, G.R. |date=September 1956 |title=On synchrotron radiation from Messier&nbsp;87 |journal=The Astrophysical Journal |volume=124 |pages=416–429 |doi=10.1086/146237 |bibcode=1956ApJ...124..416B|doi-access=free }}</ref>

<ref name=nature355_804>{{cite journal |author=Sparks, W.B. |author2=Fraix-Burnet, D. |author3=Macchetto, F. |author4=Owen, F.N. |date=February 1992 |title=A counterjet in the elliptical galaxy M87 |journal=[[Nature (journal)|Nature]] |volume=355 |issue=6363 |pages=804–806 |doi=10.1038/355804a0 |bibcode=1992Natur.355..804S|s2cid=4332596 }}</ref>

<ref name=cooke2005>{{cite book |author=Cooke, A. |date=2005 |title=Visual Astronomy Under Dark Skies: A new approach to observing deep space |series=Patrick Moore's practical astronomy series |location=London, United Kingdom |publisher=Springer-Verlag |pages=5–37 |isbn=978-1-85233-901-2}}</ref>

<ref name=science287_5450_79>{{cite journal |author=Bland-Hawthorn, J. |author2=Freeman, K. |date=January 2000 |title=The baryon halo of the Milky Way: A fossil record of its formation |journal=[[Science (journal)|Science]] |volume=287 |issue=5450 |pages=79–84 |doi=10.1126/science.287.5450.79
|pmid=10615053 |bibcode = 2000Sci...287...79B}}</ref>

<ref name=aaa518_1III>{{cite journal |author=Clemens, M. S. |display-authors=etal |date=July 2010 |title=The Herschel Virgo Cluster Survey. III. A constraint on dust grain lifetime in early-type galaxies |journal=Astronomy and Astrophysics |volume=518 |pages=L50 |doi=10.1051/0004-6361/201014533 |bibcode=2010A&A...518L..50C |arxiv=1005.3056|s2cid=119280598 }}</ref>

<ref name=jones2004>{{cite book |author=Jones, M. H. |author2=Lambourne, R. J. |author3=Adams, D. J. |date=2004 |title=An introduction to galaxies and cosmology |publisher=Cambridge University Press |page=13 |isbn=978-0-521-54623-2 }}</ref>

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|doi=10.1007/BFb0106442|s2cid=18989637 }}</ref>

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<ref name=Peterson2001>{{cite conference |author=Peterson, B.M. |date=26–30 June 2000 |title=Variability of active galactic nuclei |book-title=Advanced Lectures on the Starburst-AGN Connection |pages=3–68 |location=Tonantzintla, Mexico |editor=Aretxaga, I.|editor-link=Itziar Aretxaga |editor2=Kunth, D. |editor3=Mújica, R. |publisher=[[World Scientific]] |isbn=978-981-02-4616-7 |arxiv=astro-ph/0109495 |bibcode=2001sac..conf....3P |doi=10.1142/9789812811318_0002}}</ref>

<ref name=BHImage>{{cite journal |author=The Event Horizon Telescope Collaboration |year=2019 |title=First M87 Event Horizon Telescope results. IV. Imaging the central supermassive black hole |journal=The Astrophysical Journal |volume=875 |issue=1 |page=L4 |issn=2041-8213 |doi=10.3847/2041-8213/ab0e85 |arxiv=1906.11241 |bibcode=2019ApJ...875L...4E |s2cid=146068771 |url=https://repository.ubn.ru.nl/bitstream/2066/202543/1/202543.pdf |doi-access=free }}</ref>

<ref name=EHT2019>{{cite magazine |author=Jeffrey, K. |date=10 April 2019 |title=These are the first pictures of a black hole – And that's a big, even supermassive, deal |magazine=[[Time (magazine)|Time]] |url=https://time.com/5566225/first-black-hole-picture-photo/ |access-date=10 April 2019}}</ref>

<ref name=OAM_MNRASL2019>{{cite journal |author1=Tamburini, F. |author2=Thidé, B. |author3=Della Valle, M. |date=November 2019 |title=Measurement of the spin of the M87 black hole from its observed twisted light |journal=Monthly Notices of the Royal Astronomical Society Letters |volume=492 |issue=1 |pages=L22–L27 |doi=10.1093/mnrasl/slz176 |doi-access=free |url=https://academic.oup.com/mnrasl/article-abstract/492/1/L22/5645245?redirectedFrom=fulltext |arxiv=1904.07923 }}</ref>

<ref name=AJL875-1>''see'' {{cite journal |title=First M87 Event Horizon Telescope results |journal=The Astrophysical Journal Letters |url=https://iopscience.iop.org/issue/2041-8205/875/1 |date=10 April 2019 |volume=875 |issue=1}} ''for links to papers''</ref>

<ref name="NYT-20190410a">{{cite news |last=Overbye |first=Dennis |author-link=Dennis Overbye |date=10 April 2019 |title=Black hole picture revealed for the first time |newspaper=[[The New York Times]] |quote=Astronomers at last have captured an image of the darkest entities in the cosmos. |url=https://www.nytimes.com/2019/04/10/science/black-hole-picture.html?comments#permid=31473598 |access-date=10 April 2019 }}</ref>

<ref name="APJL-20190410a">{{cite journal |author=The Event Horizon Telescope Collaboration |title=First M87 Event Horizon Telescope results. I. The shadow of the supermassive black hole |date=10 April 2019 |journal=[[The Astrophysical Journal Letters]] |volume=875 |pages=L1 |number=1 |doi=10.3847/2041-8213/ab0ec7 |arxiv=1906.11238 |bibcode=2019ApJ...875L...1E |s2cid=145906806 |url=https://research.aalto.fi/files/33507093/ELEC_Savolainen_The_Event_Horizon_Telescope_Collaboration_2019_ApJL_875_L1.pdf |doi-access=free }}</ref>

<ref name="NASA-20190410">{{cite press release |last=Landau |first=Elizabeth |date=10 April 2019 |publisher=[[NASA]] |title=Black Hole Image Makes History |url=https://www.jpl.nasa.gov/news/news.php?feature=7372 |access-date=10 April 2019 }}</ref>

<ref name=Akiyama2015>{{cite journal | title=230&nbsp;GHz VLBI observations of M87: Event-horizon-scale structure during an enhanced very-high-energy γ-ray state in 2012 | author=Akiyama, Kazunori | author2= Lu, Ru-Sen | author3=Fish, Vincent L | display-authors=etal| journal=The Astrophysical Journal | volume=807|issue=2 | page=150|date=July 2015 | doi=10.1088/0004-637X/807/2/150 | bibcode=2015ApJ...807..150A| hdl=1721.1/98305 | arxiv=1505.03545 | s2cid=50953437 }}</ref>

<ref name="EHT4">{{cite journal |last1=The Event Horizon Telescope Collaboration |title=First M87 Event Horizon Telescope results. VI. The shadow and mass of the central black hole |journal=The Astrophysical Journal |date=10 April 2019 |volume=875 |issue=1 |pages=L6 |doi=10.3847/2041-8213/ab1141 |arxiv=1906.11243 |bibcode=2019ApJ...875L...6E |s2cid=145969867 |url=https://repository.ubn.ru.nl/bitstream/2066/202545/1/202545.pdf |doi-access=free }}</ref>

}} <!-- end "refs=" -->

==External links==
{{Commons category|Messier 87}}
* [http://messier.seds.org/m/m087.html Messier 87], SEDS Messier pages
* [http://www.spacetelescope.org/images/?search=m87 ESA/Hubble images of M87]{{WikiSky}}
* [http://nova.astro.umd.edu/Tlusty2002/solar-abun.html Solar elemental abundances]

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{{DEFAULTSORT:Messier 87}}
[[Category:Messier 87| ]]
[[Category:Elliptical galaxies|Messier 087]]
[[Category:Peculiar galaxies|Messier 087]]
[[Category:Radio galaxies|Messier 087]]
[[Category:Virgo Cluster|Messier 087]]
[[Category:Virgo (constellation)|Messier 087]]
[[Category:Messier objects|087]]
[[Category:NGC objects|Messier 087]]
[[Category:UGC objects|07654]]
[[Category:Principal Galaxies Catalogue objects|41316]]
[[Category:Arp objects|152]]
[[Category:3C objects|274]]
[[Category:Astronomical objects discovered in 1781]]
[[Category:Discoveries by Charles Messier]]