# Messier 87

Messier 87 (also known as Virgo A or NGC 4486, generally abbreviated to M87) is a supergiant elliptical galaxy with several trillion stars in the constellation Virgo. One of the most massive galaxies in the local universe,[a] it has a large population of globular clusters — about 15,000 compared with the 150–200 orbiting the Milky Way — and a jet of energetic plasma that originates at the core and extends at least 1,500 parsecs (4,900 light-years), 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 astronomers.

Messier 87
The galactic core of Messier 87, with its blue plasma jet clearly visible (composite image of observations by the Hubble Space Telescope in visible and infrared light)
Observation data (J2000 epoch)
ConstellationVirgo
Right ascension12h 30m 49.42338s[1]
Declination+12° 23′ 28.0439″[1]
Redshift0.00428 ± 0.00002[2]
Helio radial velocity1,284 ± 5 km/s[2]
Distance16.4 ± 0.5 Mpc (53.5 ± 1.6 Mly)[3]
Apparent magnitude (V)8.6[4]
Characteristics
TypeE+0-1 pec, NLRG Sy[5]
Size980 kly (300 kpc)[6]
Apparent size (V)7.2 × 6.8 [7]
Other designations
Virgo A, Virgo X-1, NGC 4486, UGC 7654, PGC 41361, VCC 1316, Arp 152, 3C 274,[5] 3U 1228+12.[8]

The French astronomer Charles Messier discovered M87 in 1781, and cataloged it as a nebula. M87 is about 16.4 million parsecs (53 million light-years) 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 lanes. Instead, it has an almost featureless, ellipsoidal shape typical of most giant elliptical galaxies, diminishing in luminosity with distance from the center. Forming around one-sixth of its mass, M87's stars 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 April 2019. In March 2021, the EHT Collaboration presented, for the first time, a polarized-based image of the black hole which may help better reveal the forces giving rise to quasars.[12]

The galaxy is a strong source of multi-wavelength radiation, particularly radio waves. Its galactic envelope extends to a radius of about 150 kiloparsecs (490,000 light-years), where it is truncated – possibly by an encounter with another galaxy. Its interstellar medium consists of diffuse gas enriched by elements emitted from evolved stars.

## Observation history

In 1781, the French astronomer Charles Messier published a catalogue of 103 objects that had a nebulous appearance as part of a list intended to identify objects that might otherwise be confused with comets. In subsequent use, each catalogue entry was prefixed with an "M". Thus, M87 was the eighty-seventh object listed in Messier's catalogue.[13] During the 1880s, the object was included as NGC 4486 in the New General Catalogue of nebulae and star clusters assembled by the Danish-Irish astronomer John Dreyer, which he based primarily on the observations of the English astronomer John Herschel.[14]

In 1918, the American astronomer 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.[15] The following year, a supernova within M87 reached a peak photographic magnitude of 21.5, although this event was not reported until photographic plates were examined by the Russian astronomer Innokentii A. Balanowski in 1922.[16][17]

### Identification as a galaxy

In Hubble's galaxy classification scheme, M87 is an E0 galaxy

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.[18] In 1926 he produced a new categorization, distinguishing extragalactic from galactic nebulae, the former being independent star systems. M87 was classified as a type of elliptical extragalactic nebula with no apparent elongation (class E0).[19]

In 1931, Hubble described M87 as a member of the Virgo Cluster, and gave a provisional estimate of 1.8 million parsecs (5.9 million light-years) from Earth. It was then the only known elliptical nebula for which individual stars could be resolved, although it was pointed out that globular clusters would be indistinguishable from individual stars at such distances.[20] 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 then was synonym for the Milky Way.[21] M87 continued to be labelled as an extragalactic nebula at least until 1954.[22][23]

### Modern research

In 1947, a prominent radio source, Virgo A, was identified overlapping the location of M87.[24] 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 with an angular width of 2″.[22] In 1969–1970, a strong component of the radio emission was found to closely align with the optical source of the jet.[8] In 1966, the United States Naval Research Laboratory's Aerobee 150 rocket identified Virgo X-1, the first X-ray source in Virgo.[25][26] The Aerobee rocket launched from White Sands Missile Range on 7 July 1967 yielded further evidence that the source of Virgo X-1 was the radio galaxy M87.[27] Subsequent X-ray observations by the HEAO 1 and Einstein Observatory showed a complex source that included the active galactic nucleus of M87.[28] However, there is little central concentration of the X-ray emission.[8]

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 billion M solar masses.[29] 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 billion M, with 30% uncertainty.[30] Globular clusters within M87 have been used to calibrate metallicity relations as well.[31]

M87 was observed by the Event Horizon Telescope (EHT) during much of 2017.[33] The event horizon of the black hole at the center was directly imaged by the EHT,[34] then revealed in a press conference on the issue date stated, filtering out from this the first image of a black hole's shadow.[35]

## Visibility

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 Leonis).[b] The galaxy can be observed using a small telescope with a 6 cm (2.4 in) aperture, extending across an angular area of 7.2 × 6.8 arcminutes at a surface brightness of 12.9, with a very bright, 45 arcsecond core.[7] Viewing the jet is a challenge without the aid of photography.[36] Before 1991, the Russian-American astronomer Otto Struve was the only person known to have seen the jet visually, using the 254 cm (100 in) Hooker telescope.[37] In more recent years it has been observed in larger amateur telescopes under excellent conditions.[38]

## 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.[39] 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.[39][40] In the Yerkes (Morgan) scheme, M87 is classified as a type-cD galaxy.[41][42] A D galaxy has an elliptical-like nucleus surrounded by an extensive, dustless, diffuse envelope. A D type supergiant is called a cD galaxy.[43][44]

The distance to M87 has been estimated using several independent techniques. These include measurement of the luminosity of planetary nebulae, comparison with nearby galaxies whose distance is estimated using standard candles such as cepheid variables, the linear size distribution of globular clusters,[c] and the tip of the red-giant branch method using individually resolved red giant stars.[d] These measurements are consistent with each other, and their weighted average yields a distance estimate of 16.4 ± 0.5 megaparsecs (53.5 ± 1.63 million light-years).[3]

 Radiuskpc Mass×1012 M☉ 32 2.4[45] 44 3.0[46] 47 5.7[47] 50 6.0[48]

Stellar velocity map of the central region of M87, showing the motion of stars relative to Earth. Blue represents motion towards Earth and red indicates motion away, while yellow and green are in between. Image shows the aspects of a random nature among their movement.[49][50]

M87 is one of the most massive galaxies in the local Universe. Its diameter is estimated at 240,000 light-years, which is approximately double that of the Milky Way.[47] 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 32 kiloparsecs (100,000 light-years), the mass is (2.4±0.6)×1012 times the mass of the Sun,[45] which is double the mass of the Milky Way galaxy.[51] As with other galaxies, only a fraction of this mass is in the form of stars: M87 has an estimated mass to luminosity ratio of 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.[52] This ratio varies from 5 to 30, approximately in proportion to r1.7 in the region of 9–40 kiloparsecs (29,000–130,000 light-years) from the core.[46] The total mass of M87 may be 200 times that of the Milky Way.[53]

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.[54] The extended stellar envelope of this galaxy reaches a radius of about 150 kiloparsecs (490,000 light-years),[6] compared with about 100 kiloparsecs (330,000 light-years) for the Milky Way.[55] Beyond that distance the outer edge of the galaxy has been truncated by some means; possibly by an earlier encounter with another galaxy.[6][56] There is evidence of linear 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.[57] 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.[58] M87 is estimated to have at least 50 satellite galaxies, including NGC 4486B and NGC 4478.[59][60]

The spectrum of the nuclear region of M87 shows the emission lines 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".[61][62] 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[61][62] or photoionization in the inner region powered by the jet.[63]

Elliptical galaxies such as M87 are believed to form as the result of one or more mergers of smaller galaxies.[64] They generally contain relatively little cold 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.[65] 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 mixing of a disrupted galaxy.[66][67]

## Components

### Supermassive black hole M87*

The Event Horizon Telescope image of the core of M87 using 1.3 mm microwaves. The central dark spot is the shadow of M87* and is larger than the black hole's event horizon.
A view of the M87* supermassive black hole in polarised light, taken by Event Horizon Telescope and revealed on 24 March 2021. The direction of lines atop the total intensity mark the direction of the electromagnetic wave electric vector oscillations.

Composite image showing how the M87 system looked, across the entire electromagnetic spectrum, during the Event Horizon Telescope's April 2017 campaign to take the first image of a black hole. Requiring 19 different facilities on the Earth and in space, this image reveals the enormous scales spanned by the black hole and its forward-pointing jet. The upper left of the figure is an image taken by ALMA, showing the larger-scale jet observed on the same scale as the visible image taken by the Hubble Space Telescope and the X-ray image by Chandra (upper right).[68]

The core of the galaxy contains a supermassive black hole (SMBH), designated M87*,[32][69] whose mass is billions of times that of the Earth's Sun; estimates had ranged from (3.5±0.8)×109 M[70] to (6.6±0.4)×109 M,[70] surpassed by 7.22+0.34
−0.40
×109
M in 2016.[71] In April 2019, the Event Horizon Telescope collaboration released measurements of the black hole's mass as (6.5 ± 0.2stat ± 0.7sys) × 109 M.[72] This is one of the 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 1,000 km/s,[73] and spans a maximum diameter of 0.12 pc (25,000 AU; 0.39 ly; 3.7 trillion km).[74] By comparison, Pluto averages 39 AU (0.00019 pc; 5.8 billion km) from the Sun. Gas accretes onto the black hole at an estimated rate of one solar mass every ten years (about 90 Earth masses per day).[75] The Schwarzschild radius of the black hole is 5.9×10−4 parsecs (1.9×10−3 light-years), or 18 billion km, which is around 120 times the Earth–Sun distance (120 AU).[76] The diameter of the accretion disk, as seen from Earth, is 42 μas (microarcsecond) and the diameter of the back hole itself is 15 μas. 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 seven parsecs (23 light-years).[77] 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.[77][78] However, a 2011 study did not find any statistically significant displacement,[79] 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.[80]

This black hole is the first to be imaged. Data to produce the image were taken in April 2017, the image was produced during 2018 and was published on 10 April 2019.[35][81][82] The image shows the shadow of the black hole,[83] surrounded by an asymmetric emission ring with a diameter of 3.36×10−3 parsecs (0.0110 ly). The shadow radius is 2.6 times that of the black hole's Schwarzschild radius.[84] The rotation parameter was estimated at a = 0.9 ± 0.1 , corresponding to a rotation speed ≈ 0.4 c .[85]

After the black hole had been imaged, it was named Pōwehi, a Hawai'ian word meaning "the adorned fathomless dark creation", taken from the ancient creation chant Kumulipo.[86]

On 24 March 2021, the Event Horizon Telescope collaboration revealed a unprecedented unique view of the M87 black hole shadow: how it looks in polarized light.[87] 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.[88] Knowing those is essential to understand how M87 supermassive black hole is launching jets of magnetized plasma which expand at relativistic speed beyond the M87 galaxy.

On 14 April 2021, astronomers further reported that the M87 black hole and its surrounding was studied during Event Horizon Telescope 2017 observing run also by many multi-wavelength observatories from around the world.[89]

### Jet

The jet of matter is ejected from M87 at nearly the speed of light, and stretches 1.5 kpc (5 kly) from the galactic core.
In this X-ray (Chandra) and radio (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.

The relativistic jet of matter emerging from the core extends at least 1.5 kiloparsecs (5,000 light-years) from the nucleus and consists of matter ejected from a supermassive black hole. The jet is highly collimated, appearing constrained to an angle of 60° within 0.8 pc (2.6 light-years) of the core, to about 16° at two parsecs (6.5 light-years), and to 6–7° at twelve parsecs (39 light-years).[90] Its base has the diameter of 5.5 ± 0.4 Schwarzschild radii, and is probably powered by a prograde accretion disk around the spinning supermassive black hole.[90] The German-American astronomer Walter Baade found that light from the jet was plane polarized, which suggests that the energy is generated by the acceleration of electrons moving at relativistic velocities in a magnetic field. The total energy of these electrons is estimated at 5.1 × 1056 ergs[91] (5.1 × 1049 joules or 3.2 × 1068 eV). This is roughly 1013 times the energy produced in the entire Milky Way in one second, which is estimated at 5 × 1036 joules.[92] 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.[93][94] The jet is precessing, causing the outflow to form a helical pattern out to 1.6 parsecs (5.2 light-years).[74] Lobes of expelled matter extend out to 80 kiloparsecs (260,000 light-years).[95]

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. Detection of such motion is used to support the theory that quasars, BL Lacertae objects and radio galaxies may all be the same phenomenon, known as active galaxies, viewed from different perspectives.[96][97] It is proposed that the nucleus of M87 is a BL Lacertae object (of lower luminosity than its surrounds) seen from a relatively large angle. Flux variations, characteristic of the BL Lacertae objects, have been observed in M87.[98][99]

Radio wavelength image of M87 showing strong radio emission from the core

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 million years. One of the rings, caused by a major eruption, is a shock wave 26 kiloparsecs (85,000 light-years) in diameter around the black hole. Other features observed include narrow X-ray-emitting filaments up to 31 kiloparsecs (100,000 light-years) long, and a large cavity in the hot gas caused by a major eruption 70 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 rays, 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.[100] In general, the smaller the diameter of the emission source, the faster the variation in flux.[100][101]

M87 in infrared showing shocks produced by the jets
Spiral flow of the black hole-powered jet[102]

A knot of matter in the jet (designated HST-1), about 65 parsecs (210 light-years) 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,[103] while the X-ray emission has since been decaying in a variable manner.[104]

The interaction of relativistic jets of plasma emanating from the core with the surrounding medium gives rise to radio lobes in active galaxies. The lobes occur in pairs and are often symmetrical.[105] The two radio lobes of M87 together span about 80 kiloparsecs; the inner parts, extending up to 2 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.[106][107]

### 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.[108][109] 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 supernovae.[108]

The distribution of oxygen is roughly uniform throughout, at about half of the solar value (i.e., oxygen abundance in the Sun), while iron distribution peaks near the center where it approaches the solar iron value.[109][110] Since oxygen is produced mainly by core-collapse supernovae, which occur during the early stages of galaxies, and mostly in outer star-forming regions,[108][109][110] the distribution of these elements suggests an early enrichment of the interstellar medium from core-collapse supernovae and a continuous contribution from type Ia supernovae throughout the history of M87.[108] The contribution of elements from these sources was much lower than in the Milky Way.[108]

 Element Abundance(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 μm. Normally, this may be an indication of thermal emission by warm dust.[111] 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 million years because of the X-ray emission from the core.[112] This dust may be destroyed by the hostile environment or expelled from the galaxy.[113] The combined mass of dust in M87 is no more than 70,000 times the mass of the Sun.[112] By comparison, the Milky Way's dust equals about a hundred million (108) solar masses.[114]

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.[115] These filaments have an estimated mass of about 10,000 M.[54][115] Surrounding the galaxy is an extended corona with hot, low-density gas.[116]

### Globular clusters

M87 has an abnormally large population of globular clusters. A 2006 survey out to an angular distance of 25 from the core estimates that there are 12,000 ± 800 globular clusters in orbit around M87,[117] 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 parsecs. The size of the M87 clusters gradually increases with distance from the galactic center.[118] Within a four-kiloparsec (13,000-light-year) 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.[116] Clusters with low metallicity are somewhat larger than metal-rich clusters.[118] In 2014, HVGC-1, the first hypervelocity globular cluster, was discovered escaping from M87 at 2,300 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.[119]

Almost a hundred ultra-compact dwarfs have been identified in M87. They resemble globular clusters but have a diameter of ten parsecs (33 light-years) or more, much larger than the three-parsec (9.8-light-year) maximum of globular clusters. It is unclear whether they are dwarf galaxies captured by M87 or a new class of massive globular cluster.[120]

## Environment

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.

M87 is near (or at) the center of the Virgo Cluster,[42] a closely compacted structure of about 2,000 galaxies.[121] This forms the core of the larger Virgo Supercluster, of which the Local Group (including the Milky Way) is an outlying member.[6] It is organized into at least three distinct subsystems associated with the three large galaxies — M87, M49 and M86 — with the core subgroup including M87 (Virgo A) and M49 (Virgo B).[122] There is a preponderance of elliptical and S0 galaxies around M87.[123] A chain of elliptical galaxies roughly aligns with the jet.[123] 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.[6] 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.[111] The combined mass of the cluster is estimated to be 0.15 to 1.5 × 1015 M.[121]

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 M84, as evidenced by the truncation of M87's outer halo by 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.[6]

## Notes

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 million to a billion light-years.[9][10][11]
2. ^ Epsilon Virginis is at celestial coordinates α=13ʰ02ᵐ, δ=+10°57′; Denebola is at α=11ʰ49ᵐ, δ=+14°34′. The midpoint of the pair is at α=12ʰ16ᵐ, δ=12°45′. Compare to the coordinates of Messier 87: α=12ʰ31ᵐ, δ=+12°23′ .
3. ^ This yields a distance of 16.4 ± 2.3 megaparsecs (53.5 ± 7.50 million light-years).[3]
4. ^ This yields a distance of 16.7 ± 0.9 megaparsecs (54.5 ± 2.94 million light-years).[3]

## References

1. ^ a b Lambert, S.B.; Gontier, A.-M. (January 2009). "On radio source selection to define a stable celestial frame". Astronomy and Astrophysics. 493 (1): 317–323. Bibcode:2009A&A...493..317L. doi:10.1051/0004-6361:200810582. See the tables in particular.
2. ^ a b Cappellari, Michele; et al. (11 May 2011). "The ATLAS3D project – I. A volume-limited sample of 260 nearby early-type galaxies: science goals and selection criteria". Monthly Notices of the Royal Astronomical Society. 413 (2): 813–836. arXiv:1012.1551. Bibcode:2011MNRAS.413..813C. doi:10.1111/j.1365-2966.2010.18174.x. S2CID 15391206.
3. ^ a b c d Bird, S.; Harris, W.E.; Blakeslee, J. P.; Flynn, C. (December 2010). "The inner halo of M87: A first direct view of the red-giant population". Astronomy and Astrophysics. 524: A71. arXiv:1009.3202. Bibcode:2010A&A...524A..71B. doi:10.1051/0004-6361/201014876. S2CID 119281578.
4. ^ "Messier 87". SEDS Messier Catalog. Retrieved 30 April 2022.
5. ^ a b "Results for NGC 4486". NASA/IPAC Extragalactic Database. California Institute of Technology. Retrieved 8 April 2019.
6. Doherty, M.; Arnaboldi, M.; Das, P.; Gerhard, O.; Aguerri, J.A.L.; Ciardullo, R.; et al. (August 2009). "The edge of the M87 halo and the kinematics of the diffuse light in the Virgo cluster core". Astronomy and Astrophysics. 502 (3): 771–786. arXiv:0905.1958. Bibcode:2009A&A...502..771D. doi:10.1051/0004-6361/200811532. S2CID 17110964.
7. ^ a b Luginbuhl, C. B.; Skiff, B. A. (1998). Observing Handbook and Catalogue of Deep-Sky Objects (2nd ed.). Cambridge, United Kingdom: Cambridge University Press. p. 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"
8. ^ a b c Turland, B. D. (February 1975). "Observations of M87 at 5 GHz with the 5-km telescope". Monthly Notices of the Royal Astronomical Society. 170 (2): 281–294. Bibcode:1975MNRAS.170..281T. doi:10.1093/mnras/170.2.281.
9. ^ "The Local Universe". Division H. International Astronomical Union. University of Leiden. Retrieved 1 May 2018.
10. ^ Courtois, H.M.; Pomarède, D.; Tully, R.B.; Hoffman, Y.; Courtois, D. (August 2013). "Cosmography of the local universe". The Astronomical Journal. 146 (3): 69. arXiv:1306.0091. Bibcode:2013AJ....146...69C. doi:10.1088/0004-6256/146/3/69. S2CID 118625532.
11. ^ "Local Universe". Department of Astronomy. University of Wisconsin-Madison. Retrieved 1 May 2018.
12. ^ Overbye, Dennis (24 March 2021). "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". The New York Times. Archived from the original on 28 December 2021. Retrieved 25 March 2021.
13. ^ Basu, B.; Chattopadhyay, T.; Biswas, S.N. (2010). An Introduction to Astrophysics (2nd ed.). New Delhi: PHI Learning Pvt. Ltd. p. 278. ISBN 978-81-203-4071-8.
14. ^ Dreyer, J. L. E. (1888). "A New General Catalogue of Nebulae and Clusters of Stars, being the Catalogue of the late Sir John F.W. Herschel, Bart., revised, corrected, and enlarged". Memoirs of the Royal Astronomical Society. 49: 1–237. Bibcode:1888MmRAS..49....1D.
15. ^ Curtis, H. D. (1918). "Descriptions of 762 Nebulae and Clusters Photographed with the Crossley Reflector". Publications of the Lick Observatory. 13: 9–42. Bibcode:1918PLicO..13....9C.
16. ^ Hubble, E. (October 1923). "Messier 87 and Belanowsky's Nova". Publications of the Astronomical Society of the Pacific. 35 (207): 261–263. Bibcode:1923PASP...35..261H. doi:10.1086/123332.
17. ^ Shklovskii, I. S. (August 1980). "Supernovae in Multiple Systems". Soviet Astronomy. 24: 387–389. Bibcode:1980SvA....24..387S.
18. ^ Hubble, E. P. (October 1922). "A general study of diffuse galactic nebulae". The Astrophysical Journal. 56: 162–199. Bibcode:1922ApJ....56..162H. doi:10.1086/142698.
19. ^ Hubble, E. P. (December 1926). "Extragalactic nebulae". The Astrophysical Journal. 64: 321–369. Bibcode:1926ApJ....64..321H. doi:10.1086/143018.
20. ^ Hubble, E.; Humason, M. L. (July 1931). "The Velocity-Distance Relation among Extra-Galactic Nebulae". The Astrophysical Journal. 74: 43–80. Bibcode:1931ApJ....74...43H. doi:10.1086/143323.
21. ^ Hubble, E.P. (1936). The Realm of the Nebulae. Mrs. Hepsa Ely Silliman Memorial Lectures. Vol. 25. New Haven, CT: Yale University Press. ISBN 9780300025002. OCLC 611263346. Archived from the original on 5 September 2015.(pp. 16–17)
22. ^ a b Baade, W.; Minkowski, R. (January 1954). "On the Identification of Radio Sources". The Astrophysical Journal. 119: 215–231. Bibcode:1954ApJ...119..215B. doi:10.1086/145813.
23. ^ Burbidge, G.R. (September 1956). "On synchrotron radiation from Messier 87". The Astrophysical Journal. 124: 416–429. Bibcode:1956ApJ...124..416B. doi:10.1086/146237.
24. ^ Stanley, G. J.; Slee, O. B. (June 1950). "Galactic Radiation at Radio Frequencies. II. The Discrete Sources". Australian Journal of Scientific Research A. 3 (2): 234–250. Bibcode:1950AuSRA...3..234S. doi:10.1071/ch9500234.
25. ^ Drake, S. A. "A Brief History of High-Energy Astronomy: 1965–1969". NASA HEASARC. Archived from the original on 14 May 2012. Retrieved 28 October 2011.
26. ^ Charles, P. A.; Seward, F. D. (1995). Exploring the X-ray universe. Cambridge, United Kingdom: Cambridge University Press. p. 9. ISBN 978-0-521-43712-7.
27. ^ Bradt, H.; Naranan, S.; Rappaport, S.; Spada, G. (June 1968). "Celestial Positions of X-ray Sources in Sagittarius". The Astrophysical Journal. 152 (6): 1005–1013. Bibcode:1968ApJ...152.1005B. doi:10.1086/149613.
28. ^ Lea, S. M.; Mushotzky, R.; Holt, S. S. (November 1982). "Einstein Observatory solid state spectrometer observations of M87 and the Virgo cluster". Astrophysical Journal, Part 1. 262: 24–32. Bibcode:1982ApJ...262...24L. doi:10.1086/160392. hdl:2060/19820026438.
29. ^ Sargent, W.L.W.; Young, P.J.; Lynds, C.R.; Boksenberg, A.; Shortridge, K.; Hartwick, F.D.A. (May 1978). "Dynamical evidence for a central mass concentration in the galaxy M87". The Astrophysical Journal. 221: 731–744. Bibcode:1978ApJ...221..731S. doi:10.1086/156077.
30. ^ Harms, R.J.; et al. (November 1994). "HST FOS spectroscopy of M87: Evidence for a disk of ionized gas around a massive black hole". The Astrophysical Journal Letters. 435: L35–L38. Bibcode:1994ApJ...435L..35H. doi:10.1086/187588.
31. ^ Forte, Juan C.; Faifer, Favio R.; Vega, E. Irene; Bassino, Lilia P.; Smith Castelli, Analía V.; Cellone, Sergio A.; Geisler, Douglas (11 May 2013). "Multicolour–metallicity relations from globular clusters in NGC 4486 (M87)". Monthly Notices of the Royal Astronomical Society. 431 (2): 1405–1416. doi:10.1093/mnras/stt263.
32. ^ a b see "First M87 Event Horizon Telescope results". The Astrophysical Journal Letters. 875 (1). 10 April 2019 – via IOPscience. for links to papers
33. ^ "[whole issue]". Astrophysical Journal Letters. 875 (1). 10 April 2019. was dedicated to the results, published six open-access papers.[32]
34. ^ The Event Horizon Telescope Collaboration (2019). "First M87 Event Horizon Telescope results. IV. Imaging the ccentral supermassive black hole" (PDF). The Astrophysical Journal. 875 (1): L4. arXiv:1906.11241. Bibcode:2019ApJ...875L...4E. doi:10.3847/2041-8213/ab0e85. ISSN 2041-8213. S2CID 146068771.{{cite journal}}: CS1 maint: uses authors parameter (link)
35. ^ a b Jeffrey, K. (10 April 2019). "These are the first pictures of a black hole — And that's a big, even supermassive, deal". Time. Retrieved 10 April 2019.
36. ^ Cooke, A. (2005). Visual Astronomy Under Dark Skies: A new approach to observing deep space. Patrick Moore's practical astronomy series. London, United Kingdom: Springer-Verlag. pp. 5–37. ISBN 978-1-85233-901-2.
37. ^ Clark, R. N. (1990). Visual astronomy of the deep sky. Cambridge University Press. p. 153. ISBN 978-0-521-36155-2.
38. ^ "Visual observations of the M87 jet". Adventures in Deep Space. Astronomy-Mall. Archived from the original on 7 July 2011. Retrieved 7 December 2010.
39. ^ a b Park, K. S.; Chun, M. S. (June 1987). "Dynamical Structure of NGC 4486". Journal of Astronomy and Space Science. 4 (1): 35–45. Bibcode:1987JASS....4...35P.
40. ^ Jones, M. H.; Lambourne, R. J. (2004). An introduction to galaxies and cosmology. Cambridge University Press. p. 69. ISBN 978-0-521-54623-2.
41. ^ Kundu, A.; Whitmore, B. C. (2001). "New Insights from HST Studies of Globular Cluster Systems. I. Colors, Distances, and Specific Frequencies of 28 Elliptical Galaxies". The Astronomical Journal. 121 (6): 2950–2973. arXiv:astro-ph/0103021. Bibcode:2001AJ....121.2950K. doi:10.1086/321073. S2CID 19015891.
42. ^ a b Chakrabarty, D. (2007). "Mass modelling with minimum kinematic information". Monthly Notices of the Royal Astronomical Society. 377 (1): 30–40. arXiv:astro-ph/0702065. Bibcode:2007MNRAS.377...30C. doi:10.1111/j.1365-2966.2007.11583.x. S2CID 16263041.
43. ^ Oemler, A. Jr. (November 1976). "The structure of elliptical and cD galaxies". The Astrophysical Journal. 209: 693–709. Bibcode:1976ApJ...209..693O. doi:10.1086/154769.
44. ^ Whitmore, B. C. (15–17 May 1989). "Effect of the Cluster Environment on Galaxies". In William R. Oegerle; Michael J. Fitchett; Laura Danly (eds.). Clusters of galaxies: proceedings of the Clusters of Galaxies Meeting. Space Telescope Science Institute symposium series. Vol. 4. Baltimore: Cambridge University Press. p. 151. ISBN 0-521-38462-1.
45. ^ a b Wu, X.; Tremaine, S. (2006). "Deriving the Mass Distribution of M87 from Globular Clusters". The Astrophysical Journal. 643 (1): 210–221. arXiv:astro-ph/0508463. Bibcode:2006ApJ...643..210W. doi:10.1086/501515. S2CID 9263634.
46. ^ a b Cohen, J. G.; Ryzhov, A. (September 1997). "The Dynamics of the M87 Globular Cluster System". The Astrophysical Journal. 486 (1): 230–241. arXiv:astro-ph/9704051. Bibcode:1997ApJ...486..230C. doi:10.1086/304518. S2CID 13517745.
47. ^ a b Murphy, J. D.; Gebhardt, K.; Adams, J. J. (March 2011). "Galaxy Kinematics with VIRUS-P: The Dark Matter Halo of M87". The Astrophysical Journal. 729 (2): 129. arXiv:1101.1957. Bibcode:2011ApJ...729..129M. doi:10.1088/0004-637X/729/2/129. S2CID 118686095.
48. ^ Merritt, D.; Tremblay, B. (December 1993). "The distribution of dark matter in the halo of M87". The Astronomical Journal. 106 (6): 2229–2242. Bibcode:1993AJ....106.2229M. doi:10.1086/116796.
49. ^ Galactic chromodynamics. ESO Picture of the Week (still image). Retrieved 14 October 2014.
50. ^ Emsellem, E.; Krajnovic, D.; Sarzi, M. (November 2014). "A kinematically distinct core and minor-axis rotation: The MUSE perspective on M87". Monthly Notices of the Royal Astronomical Society. 445 (1): L79–L83. arXiv:1408.6844. Bibcode:2014MNRAS.445L..79E. doi:10.1093/mnrasl/slu140. S2CID 18974737.
51. ^ Battaglia, G.; Helmi, A.; Morrison, H.; Harding, P.; Olszewski, E. W.; Mateo, M.; et al. (December 2005). "The radial velocity dispersion profile of the Galactic halo: Constraining the density profile of the dark halo of the Milky Way". Monthly Notices of the Royal Astronomical Society. 364 (2): 433–442. arXiv:astro-ph/0506102. Bibcode:2005MNRAS.364..433B. doi:10.1111/j.1365-2966.2005.09367.x. S2CID 15562509.
52. ^ Gebhardt, K.; Thomas, J. (2009). "The black hole mass, stellar mass-to-light ratio, and dark halo in M87". The Astrophysical Journal. 700 (2): 1690–1701. arXiv:0906.1492. Bibcode:2009ApJ...700.1690G. doi:10.1088/0004-637X/700/2/1690. S2CID 15481963.
53. ^ Leverington, D. (2000). New Cosmic Horizons: Space astronomy from the V2 to the Hubble Space Telescope. Cambridge University Press. p. 343. ISBN 978-0-521-65833-1.
54. ^ a b Burns, J. O.; White, R. A.; Haynes, M. P. (1981). "A search for neutral hydrogen in D and cD galaxies". The Astronomical Journal. 86: 1120–1125. Bibcode:1981AJ.....86.1120B. doi:10.1086/112992.
55. ^ Bland-Hawthorn, J.; Freeman, K. (January 2000). "The baryon halo of the Milky Way: A fossil record of its formation". Science. 287 (5450): 79–84. Bibcode:2000Sci...287...79B. doi:10.1126/science.287.5450.79. PMID 10615053.
56. ^ Klotz, I. (8 June 2009). "Galaxy's outer halo lopped off". Discovery. News. Archived from the original on 23 August 2009. Retrieved 25 April 2010.
57. ^ Janowiecki, S.; Mithos, J. C.; Harding, P.; Feldmeier, J.; Rudick, C.; Morrison, H. (June 2010). "Diffuse Tidal Structures in the Halos of Virgo Ellipticals". The Astrophysical Journal. 715 (2): 972–985. arXiv:1004.1473. Bibcode:2010ApJ...715..972J. doi:10.1088/0004-637X/715/2/972. S2CID 119196248.
58. ^ Gavazzi, G.; Boselli, A.; Vílchez, J.M.; Iglesias-Paramo, J.; Bonfanti, C. (September 2000). "The filament of ionized gas in the outskirt of M87". Astronomy & Astrophysics. 361: 1–4. arXiv:astro-ph/0007323. Bibcode:2000A&A...361....1G.
59. ^ Oldham, L.J.; Evans, N.W. (October 2016). "Is there substructure around M87?". Monthly Notices of the Royal Astronomical Society. 460 (1): 298–306. arXiv:1607.02477. Bibcode:2016MNRAS.462..298O. doi:10.1093/mnras/stw1574. S2CID 119307605.
60. ^ Fischer, D.; Duerbeck, H. (1998). Hubble Revisited: New images from the discovery machine. Copernicus New York. p. 73. ISBN 978-0387985510.
61. ^ a b Tsvetanov, Z.I.; Hartig, G.F.; Ford, H.C.; et al. (1999). "The Nuclear Spectrum of M87". In Röser, H.J.; Meisenheimer, K. (eds.). The Radio Galaxy Messier 87. Lecture Notes in Physics. Vol. 530. pp. 307–312. arXiv:astro-ph/9801037. Bibcode:1999LNP...530..307T. doi:10.1007/BFb0106442. ISBN 978-3-540-66209-9. S2CID 18989637.
62. ^ a b Dopita, M.A.; Koratkar, A.P.; Allen, M.G.; et al. (November 1997). "The LINER nucleus of M87: A shock-excited dissipative accretion disk". The Astrophysical Journal. 490 (1): 202–215. Bibcode:1997ApJ...490..202D. doi:10.1086/304862.
63. ^ Sabra, B.M.; Shields, J.C.; Ho, L.C.; et al. (February 2003). "Emission and Absorption in the M87 LINER". The Astrophysical Journal. 584 (1): 164–175. arXiv:astro-ph/0210391. Bibcode:2003ApJ...584..164S. doi:10.1086/345664. S2CID 16882810.
64. ^ Dehnen, Walter (15–19 September 1997). "M 87 as a Galaxy". In Hermann-Josef Röser; Klaus Meisenheimer (eds.). The radio galaxy Messier 87: proceedings of a workshop. Lecture Notes in Physics. Vol. 530. Ringberg Castle, Tegernsee, Germany: Springer. p. 31. arXiv:astro-ph/9802224. Bibcode:1999LNP...530...31D. doi:10.1007/BFb0106415. ISBN 978-3-540-66209-9.
65. ^ Steinicke, W.; Jakiel, R. (2007). Galaxies and how to observe them. Astronomers' observing guides. Springer. pp. 32–33. ISBN 978-1-85233-752-0.
66. ^ "Giant galaxy is still growing". European Southern Observatory (Press release). 25 June 2015. Archived from the original on 26 June 2015.
67. ^ Longobardi, A.; Arnaboldi, M.; Gerhard, O.; Mihos, J.C. (July 2015). "The build-up of the cD halo of M87 – evidence for accretion in the last Gyr". Astronomy and Astrophysics. 579 (3): L3–L6. arXiv:1504.04369. Bibcode:2015A&A...579L...3L. doi:10.1051/0004-6361/201526282. S2CID 118557973.
68. ^ "Telescopes unite in unprecedented observations of famous black hole" (Press release). Atacama Large Millimeter Array. Retrieved 15 April 2021.
69. ^ Lu, Donna (12 April 2019). "How do you name a black hole? It is actually pretty complicated". New Scientist. London, UK. Retrieved 12 April 2019. '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.
70. ^ a b Walsh, J.L.; Barth, A.J.; Ho, L.C.; Sarzi, M. (June 2013). "The M87 black hole mass from gas-dynamical models of Space Telescope Imaging Spectrograph observations". The Astrophysical Journal. 770 (2): 86. arXiv:1304.7273. Bibcode:2013ApJ...770...86W. doi:10.1088/0004-637X/770/2/86. S2CID 119193955.
71. ^ Oldham, L.J.; Auger, M.W. (March 2016). "Galaxy structure from multiple tracers - II. M87 from parsec to megaparsec scales". Monthly Notices of the Royal Astronomical Society. 457 (1): 421–439. arXiv:1601.01323. Bibcode:2016MNRAS.457..421O. doi:10.1093/mnras/stv2982. S2CID 119166670.
72. ^ The Event Horizon Telescope Collaboration (10 April 2019). "First M87 Event Horizon Telescope results. VI. The shadow and mass of the central black hole" (PDF). The Astrophysical Journal. 875 (1): L6. arXiv:1906.11243. Bibcode:2019ApJ...875L...6E. doi:10.3847/2041-8213/ab1141. S2CID 145969867.
73. ^ Macchetto, F.; Marconi, A.; Axon, D.J.; Capetti, A.; Sparks, W.; Crane, P. (November 1997). "The Supermassive Black Hole of M87 and the Kinematics of Its Associated Gaseous Disk". The Astrophysical Journal. 489 (2): 579–600. arXiv:astro-ph/9706252. Bibcode:1997ApJ...489..579M. doi:10.1086/304823. S2CID 18948008.
74. ^ a b Matveyenko, L. I.; Seleznev, S. V. (March 2011). "Fine core-jet structure of the galaxy M87". Astronomy Letters. 37 (3): 154–170. Bibcode:2011AstL...37..154M. doi:10.1134/S1063773711030030. S2CID 121731578.
75. ^ di Matteo, .; Allen, S.W.; Fabian, A.C.; Wilson, A.S.; Young, A.J. (2003). "Accretion onto the supermassive black hole in M87". The Astrophysical Journal. 582 (1): 133–140. arXiv:astro-ph/0202238. Bibcode:2003ApJ...582..133D. doi:10.1086/344504. S2CID 16182340.
76. ^ Akiyama, Kazunori; Lu, Ru-Sen; Fish, Vincent L; et al. (July 2015). "230 GHz VLBI observations of M87: Event-horizon-scale structure during an enhanced very-high-energy γ-ray state in 2012". The Astrophysical Journal. 807 (2): 150. arXiv:1505.03545. Bibcode:2015ApJ...807..150A. doi:10.1088/0004-637X/807/2/150. hdl:1721.1/98305. S2CID 50953437.
77. ^ a b Batcheldor, D.; Robinson, A.; Axon, D. J.; Perlman, E. S.; Merritt, D. (July 2010). "A Displaced Supermassive Black Hole in M87". The Astrophysical Journal Letters. 717 (1): L6–L10. arXiv:1005.2173. Bibcode:2010ApJ...717L...6B. doi:10.1088/2041-8205/717/1/L6. S2CID 119281754.
78. ^ Cowen, R. (9 June 2010). "Black hole shoved aside, along with 'central' dogma". Science News. Vol. 177, no. 13. p. 9. Archived from the original on 28 May 2010. Retrieved 29 May 2010.
79. ^ Gebhardt, K.; et al. (March 2011). "The Black-Hole Mass in M87 from Gemini/NIFS Adaptive Optics Observations". The Astrophysical Journal. 729 (2): 119–131. arXiv:1101.1954. Bibcode:2011ApJ...729..119G. doi:10.1088/0004-637X/729/2/119. S2CID 118368884.
80. ^ López-Navas, E.; Prieto, M.A. (2018). "The photocentre-AGN displacement: Is M87 actually harbouring a displaced supermassive black hole?". Monthly Notices of the Royal Astronomical Society. 480 (3): 4099. arXiv:1808.04123. Bibcode:2018MNRAS.480.4099L. doi:10.1093/mnras/sty2148. S2CID 118872175.
81. ^ Overbye, Dennis (10 April 2019). "Black hole picture revealed for the first time". The New York Times. Retrieved 10 April 2019. Astronomers at last have captured an image of the darkest entities in the cosmos.
82. ^ Landau, Elizabeth (10 April 2019). "Black Hole Image Makes History" (Press release). NASA. Retrieved 10 April 2019.
83. ^ Falcke, Heino; Melia, Fulvio; Agol, Eric (1 January 2000). "Viewing the shadow of the black hole at the galactic center". The Astrophysical Journal. 528 (1): L13–L16. arXiv:astro-ph/9912263. Bibcode:2000ApJ...528L..13F. doi:10.1086/312423. PMID 10587484. S2CID 119433133.
84. ^ The Event Horizon Telescope Collaboration (10 April 2019). "First M87 Event Horizon Telescope results. I. The shadow of the supermassive black hole" (PDF). The Astrophysical Journal Letters. 875 (1): L1. arXiv:1906.11238. Bibcode:2019ApJ...875L...1E. doi:10.3847/2041-8213/ab0ec7. S2CID 145906806.
85. ^ Tamburini, F.; Thidé, B.; Della Valle, M. (November 2019). "Measurement of the spin of the M87 black hole from its observed twisted light". Monthly Notices of the Royal Astronomical Society Letters. 492 (1): L22–L27. doi:10.1093/mnrasl/slz176.
86. ^ Mele, Christopher (13 April 2019). "That first black hole seen in an image is now called Pōwehi, at least in Hawaii". The New York Times. Retrieved 20 March 2021.
87. ^ Akiyama, Kazunori; et al. (Event Horizon Telescope Collaboration) (2021). "First M87 Event Horizon Telescope results. VII. Polarization of the ring". The Astrophysical Journal. 910 (1): L12. arXiv:2105.01169. Bibcode:2021ApJ...910L..12E. doi:10.3847/2041-8213/abe71d. S2CID 233851995. Retrieved 18 April 2021.
88. ^ Akiyama, Kazunori; et al. (Event Horizon Telescope Collaboration) (2021). "First M87 Event Horizon Telescope results. VIII. Magnetic field structure near the event horizon". The Astrophysical Journal. 910 (1): L13. arXiv:2105.01173. Bibcode:2021ApJ...910L..13E. doi:10.3847/2041-8213/abe4de. S2CID 233715131. Retrieved 18 April 2021.
89. ^ Edmonds, Peter; Cofield, Calla (14 April 2021). "Telescopes unite in unprecedented observations of famous black hole" (Press release). NASA. Retrieved 14 April 2021. 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.
90. ^ a b Doeleman, S.S.; Fish, V.L.; Schenck, D.E.; Beaudoin, C.; Blundell, R.; Bower, G.C.; et al. (October 2012). "Jet-Launching Structure Resolved Near the Supermassive Black Hole in M87". Science. 338 (6105): 355–358. arXiv:1210.6132. Bibcode:2012Sci...338..355D. doi:10.1126/science.1224768. PMID 23019611. S2CID 37585603.
91. ^ Baldwin, J. E.; Smith, F. G. (August 1956). "Radio emission from the extragalactic nebula M87". The Observatory. 76: 141–144. Bibcode:1956Obs....76..141B.
92. ^ van den Bergh, S. (September 1999). "The local group of galaxies". The Astronomy and Astrophysics Review. 9 (3–4): 273–318. Bibcode:1999A&ARv...9..273V. doi:10.1007/s001590050019. S2CID 119392899.
93. ^ Kovalev, Y.Y.; Lister, M.L.; Homan, D. C.; Kellermann, K. I. (October 2007). "The inner jet of the radio galaxy M87". The Astrophysical Journal. 668 (1): L27–L30. arXiv:0708.2695. Bibcode:2007ApJ...668L..27K. doi:10.1086/522603. S2CID 16498888.
94. ^ Sparks, W.B.; Fraix-Burnet, D.; Macchetto, F.; Owen, F.N. (February 1992). "A counterjet in the elliptical galaxy M87". Nature. 355 (6363): 804–06. Bibcode:1992Natur.355..804S. doi:10.1038/355804a0. S2CID 4332596.
95. ^ Klein, Uli (15–19 September 1997). "The large-scale structure of Virgo A". In Röser, Hermann-Josef; Meisenheimer, Klaus (eds.). The Radio Galaxy Messier 87. Lecture Notes in Physics. Vol. 530. Ringberg Castle, Tegernsee, Germany: Springer. pp. 56–65. Bibcode:1999LNP...530...56K. doi:10.1007/BFb0106418. ISBN 978-3-540-66209-9.
96. ^ Biretta, J.A.; Sparks, W.B.; Macchetto, F. (August 1999). "Hubble Space Telescope Observations of Superluminal Motion in the M87 Jet". The Astrophysical Journal. 520 (2): 621–626. Bibcode:1999ApJ...520..621B. doi:10.1086/307499.
97. ^ Biretta, J. (6 January 1999). "Hubble detects faster-than-light motion in Galaxy M87". Baltimore, Maryland: Space Telescope Science Institute. Retrieved 21 March 2018.
98. ^ Tsvetanov, Z.I.; Hartig, G.F.; Ford, H.C.; Dopita, M.A.; Kriss, G.A.; Pei, Y.C.; et al. (February 1998). "M87: A misaligned BL Lacertae object?". The Astrophysical Journal. 493 (2): L83–L86. arXiv:astro-ph/9711241. Bibcode:1998ApJ...493L..83T. doi:10.1086/311139. S2CID 118576032.
99. ^ Reimer, A.; Protheroe, R.J.; Donea, A.-C. (July 2003). "M87 as a Misaligned Synchrotron-Proton Blazar". Proceedings of the 28th International Cosmic Ray Conference. 5: 2631–2634. Bibcode:2003ICRC....5.2631R.
100. ^ a b Wirsing, B. (26 October 2006). "Discovery of Gamma Rays from the Edge of a Black Hole". Max Planck Society. Archived from the original on 3 January 2011. Retrieved 3 December 2010.
101. ^ Peterson, B.M. (26–30 June 2000). "Variability of active galactic nuclei". In Aretxaga, I.; Kunth, D.; Mújica, R. (eds.). Advanced Lectures on the Starburst-AGN Connection. Tonantzintla, Mexico: World Scientific. pp. 3–68. arXiv:astro-ph/0109495. Bibcode:2001sac..conf....3P. doi:10.1142/9789812811318_0002. ISBN 978-981-02-4616-7.
102. ^ "Hubble follows spiral flow of black-hole-powered jet" (Press release). European Space Agency / Hubble Space Telescope Science Institute. Archived from the original on 31 August 2013. Retrieved 6 September 2013.
103. ^ Harris, D.E.; Cheung, C.C.; Biretta, J.A.; Sparks, W.B.; Junor, W.; Perlman, E.S.; Wilson, A.S. (2006). "The Outburst of HST-1 in the M87 Jet". The Astrophysical Journal. 640 (1): 211–218. arXiv:astro-ph/0511755. Bibcode:2006ApJ...640..211H. doi:10.1086/500081. S2CID 17268539.
104. ^ Harris, D. E.; Cheung, C. C.; Stawarz, L. (July 2009). "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". The Astrophysical Journal. 699 (1): 305–314. arXiv:0904.3925. Bibcode:2009ApJ...699..305H. doi:10.1088/0004-637X/699/1/305. S2CID 14475336.
105. ^ Schneider, P. (2006). Extragalactic Astronomy and Cosmology: An introduction (1st ed.). Heidelberg, Germany: Springer-Verlag. p. 178. ISBN 978-3-642-06971-0.
106. ^ Owen, F.N.; Eilek, J.A.; Kassim, N.E. (November 2000). "M87 at 90 centimeters: A different picture". The Astrophysical Journal. 543 (2): 611–619. arXiv:astro-ph/0006150. Bibcode:2000ApJ...543..611O. doi:10.1086/317151. S2CID 15166238.
107. ^ "M87–Giant Elliptical Galaxy". Cool Cosmos. Caltech. Archived from the original on 15 June 2018. Retrieved 22 March 2018.
108. Werner, N.; Böhringer, H.; Kaastra, J. S.; de Plaa, J.; Simionescu, A.; Vink, J. (November 2006). "XMM-Newton high-resolution spectroscopy reveals the chemical evolution of M87". Astronomy and Astrophysics. 459 (2): 353–360. arXiv:astro-ph/0608177. Bibcode:2006A&A...459..353W. doi:10.1051/0004-6361:20065678. S2CID 18790420.
109. ^ a b c Werner, N.; Durret, F.; Ohashi, T.; Schindler, S.; Wiersma, R.P.C. (February 2008). "Observations of metals in the intra-cluster medium". Space Science Reviews. 134 (1–4): 337–362. arXiv:0801.1052. Bibcode:2008SSRv..134..337W. doi:10.1007/s11214-008-9320-9. S2CID 15906129.
110. ^ a b Finoguenov, A.; Matsushita, K.; Böhringer, H.; Ikebe, Y.; Arnaud, M. (January 2002). "X-ray evidence for spectroscopic diversity of type Ia supernovae: XMM observation of the elemental abundance pattern in M87". Astronomy and Astrophysics. 381 (1): 21–31. arXiv:astro-ph/0110516. Bibcode:2002A&A...381...21F. doi:10.1051/0004-6361:20011477. S2CID 119426359.
111. ^ a b Shi, Y.; Rieke, G.H.; Hines, D.C.; Gordon, K.D.; Egami, E. (2007). "Thermal and Nonthermal Infrared Emission from M87". The Astrophysical Journal. 655 (2): 781–789. arXiv:astro-ph/0610494. Bibcode:2007ApJ...655..781S. doi:10.1086/510188. S2CID 14424125.
112. ^ a b Baes, M.; et al. (July 2010). "The Herschel Virgo Cluster Survey. VI. The far-infrared view of M87". Astronomy and Astrophysics. 518: L53. arXiv:1005.3059. Bibcode:2010A&A...518L..53B. doi:10.1051/0004-6361/201014555. S2CID 27004145.
113. ^ Clemens, M. S.; et al. (July 2010). "The Herschel Virgo Cluster Survey. III. A constraint on dust grain lifetime in early-type galaxies". Astronomy and Astrophysics. 518: L50. arXiv:1005.3056. Bibcode:2010A&A...518L..50C. doi:10.1051/0004-6361/201014533. S2CID 119280598.
114. ^ Jones, M. H.; Lambourne, R. J.; Adams, D. J. (2004). An introduction to galaxies and cosmology. Cambridge University Press. p. 13. ISBN 978-0-521-54623-2.
115. ^ a b Ford, H.C.; Butcher, H. (October 1979). "The system of filaments in M87 – Evidence for matter falling into an active nucleus". Astrophysical Journal Supplement Series. 41: 147–172. Bibcode:1979ApJS...41..147F. doi:10.1086/190613.
116. ^ a b Harris, William E.; Harris, Gretchen L. H.; McLaughlin, Dean E. (May 1998). "M87, Globular Clusters, and Galactic Winds: Issues in Giant Galaxy Formation". The Astronomical Journal. 115 (5): 1801–1822. arXiv:astro-ph/9801214. Bibcode:1998AJ....115.1801H. doi:10.1086/300322. S2CID 119490384. The authors give a metallicity of:
${\displaystyle {\begin{smallmatrix}\left[{\frac {Fe}{H}}\right]\ =\ -0.3\end{smallmatrix}}}$
within a 3-kiloparsec radius of the galactic core.
117. ^ Tamura, N.; Sharples, R.M.; Arimoto, N.; Onodera, M.; Ohta, K.; Yamada, Y. (2006). "A Subaru/Suprime-Cam wide-field survey of globular cluster populations around M87 – I. Observation, data analysis and luminosity function". Monthly Notices of the Royal Astronomical Society. 373 (2): 588–600. arXiv:astro-ph/0609067. Bibcode:2006MNRAS.373..588T. doi:10.1111/j.1365-2966.2006.11067.x. S2CID 15127905.
118. ^ a b Madrid, J.P.; Harris, W.E.; Blakeslee, J.P.; Gómez, M. (2009). "Structural Parameters of the Messier 87 Globular Clusters". The Astrophysical Journal. 705 (1): 237–244. arXiv:0909.0272. Bibcode:2009ApJ...705..237M. doi:10.1088/0004-637X/705/1/237. S2CID 15019649. See Fig. 6. for a plot of the effective cluster radius versus galactocentric distance.
119. ^ Caldwell, N.; Strader, J.; Romanowsky, A.J.; Brodie, J.P.; Moore, B.; Diemand, J.; Martizzi, D. (May 2014). "A globular cluster toward M87 with a radial velocity < −1000 km/s: The first hypervelocity cluster". The Astrophysical Journal Letters. 787 (1): L11. arXiv:1402.6319. Bibcode:2014ApJ...787L..11C. doi:10.1088/2041-8205/787/1/L11 (inactive 28 February 2022).{{cite journal}}: CS1 maint: DOI inactive as of February 2022 (link)
120. ^ Zhang, H.X.; Peng, E.W.; Côté, P.; Liu, C.; Ferrarese, L.; Cuillandre, J.-C.; et al. (March 2015). "The Next Generation Virgo Cluster Survey. VI. The kinematics of ultra-compact dwarfs and globular clusters in M87". The Astrophysical Journal. 802 (1): 30. arXiv:1501.03167. Bibcode:2015ApJ...802...30Z. doi:10.1088/0004-637X/802/1/30. S2CID 73517961.
121. ^ a b Côté, P.; et al. (July 2004). "The ACS Virgo Cluster Survey. I. Introduction to the survey". The Astrophysical Journal Supplement Series. 153 (1): 223–242. arXiv:astro-ph/0404138. Bibcode:2004ApJS..153..223C. doi:10.1086/421490. S2CID 18021414.
122. ^ "Virgo cluster". NASA-IPAC Extragalactic Database (NED). NASA. Archived from the original on 10 November 2013. Retrieved 25 December 2012.
123. ^ a b Binggeli, B.; Tammann, G.A.; Sandage, A. (August 1987). "Studies of the Virgo cluster. VI – Morphological and kinematical structure of the Virgo cluster". The Astronomical Journal. 94: 251–277. Bibcode:1987AJ.....94..251B. doi:10.1086/114467.