Messier 87

From Wikipedia, the free encyclopedia
  (Redirected from Elliptical Galaxy M87)
Jump to: navigation, search
Messier 87
Messier 87 Hubble WikiSky.jpg
Messier 87 as seen by the Hubble Space Telescope
Observation data
Epoch J2000
Constellation Virgo
Right ascension 12h 30m 49.42338s[1]
Declination +12° 23′ 28.0439″[1]
Apparent dimension (V) 7.2 × 6.8 moa[2]
Apparent magnitude (V) 9.59[3]
Type E+0-1 pec, NLRG Sy[3]
Heliocentric radial velocity 1307 ± 7[3] km/s
Redshift 0.004360 ± 0.000022[3]
Galactocentric velocity 1254 ± 7[3] km/s
Distance 53.5 ± 1.63 Mly (16.40 ± 0.50 Mpc)[4]
Other designations
Virgo A, Virgo X-1, NGC 4486, UGC 7654, PGC 41361, VCC 1316, Arp 152, 3C 274,[3] 3U 1228+12.[5]
Database references
See also: Galaxy, List of galaxies

Messier 87 (also known as Virgo A or NGC 4486, generally abbreviated to M87) is a supergiant elliptical galaxy in the constellation Virgo. One of the most massive galaxies in the local Universe,[a] it is notable for its large population of globular clusters—about 12,000 compared to the 150–200 orbiting the Milky Way—and its jet of energetic plasma that originates at the core and extends at least 1,500 parsecs (4,900 light-years), travelling at relativistic speed. It is one of the brightest radio sources in the sky, and a popular target for both amateur and professional astronomers.

The French astronomer Charles Messier discovered M87 in 1781, and catalogued it as a nebulous feature while searching for objects that would otherwise confuse comet hunters. M87 is located about 16.4 million parsecs (53.5 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 galaxy is a strong source of multiwavelength radiation, particularly radio waves. Its galactic envelope extends to a radius of about 150 kiloparsecs (490 thousand 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[edit]

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 member of Messier's catalogue.[9] 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.[10]

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.[11] 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 (fr; ru) in 1922.[12][13]

Identification as galaxy[edit]

 Hubble classified galaxies according to their shape: ellipticals, lenticulars and spirals. Ellipticals and spirals have further categories
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.[14] 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).[15]

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.[16] 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.[17] M87 continued to be labelled as an extragalactic nebula at least until 1954.[18][19]

Images showing helical flow of matter in M87 jet
Spiral flow of the black-hole-powered jet, imaged with the Hubble Space Telescope[20]

Modern research[edit]

In 1947, a prominent radio source, Virgo A, was identified overlapping the location of M87.[21] 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″.[18] In 1969–70, a strong component of the radio emission was found to closely align with the optical source of the jet.[5]

In 1966, the United States Naval Research Laboratory's Aerobee 150 rocket identified Virgo X-1, the first X-ray source in Virgo.[22][23] 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.[24] Subsequent X-ray observations by the HEAO 1 and Einstein Observatory showed a complex source that included the active galactic nucleus of M87.[25] However, there is little central concentration of the X-ray emission.[5]

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 5 billion solar masses.[26] 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 solar masses, with 30% uncertainty.[27]


Area in constellation Virgo around M87

M87 is located near the high declination border of the Virgo constellation, next to the constellation of Coma Berenices. It lies along the line between the stars Epsilon Virginis and Denebola.[b] At an apparent magnitude of 9.59, 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 with a bright, 45 arcsecond core.[2] Viewing the jet is a challenge without the aid of photography.[28] 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.[29] In recent years it has been observed in larger amateur telescopes under excellent conditions.[30]


Central bright region of M87 is surrounded by diffuse, fainter halo
Huge halo around Messier 87[31]

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.[32] 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.[32][33] In the Yerkes (Morgan) scheme, M87 is classified as a type-cD galaxy.[34][35] A D galaxy has an elliptical-like nucleus surrounded by an extensive, dustless, diffuse envelope. A D type supergiant is called a cD galaxy.[36][37]

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).[4]

Enclosed mass
×1012 M
32 2.4[38]
44 3.0[39]
47 5.7[40]
50 6.0[41]

M87 is one of the most massive galaxies in the local Universe.[40] It spans a diameter of 120 thousand light-years, about the same as the Milky Way, but M87 is a spheroid, not a flat spiral. The mass of M87 within a radius (r) of 9–40 kiloparsecs (29–130 thousand light-years) from the core steadily increases roughly in proportion to r1.7.[39] Within a radius of 32 kiloparsecs (100 thousand light-years), the mass is (2.4 ± 0.6) × 1012 times the mass of the Sun,[38] which is double the mass of the Milky Way galaxy.[42] 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, about one part in six of the galaxy's mass is in the form of stars that radiate energy.[43] The total mass of M87 may be 200 times that of the Milky Way.[44]

stellar velocities in M87 are somewhat random, as opposed to more circular velocities in spirals
Stellar velocity map of the central region of M87, showing the motion of stars relative to Earth. Blue patches represent motion towards the Earth and red ones away from the Earth, while yellow and green are in between the two extremes. The map signifies random motion of the stars.[45][46]

Gas is infalling into the galaxy at the rate of two to three solar masses per year, most of which may be accreted onto the core region.[47] The extended stellar envelope of this galaxy reaches a radius of about 150 kiloparsecs (490 thousand light-years),[48] compared to about 100 kiloparsecs (330 thousand light-years) for the Milky Way.[49] Beyond that distance the outer edge of the galaxy has been truncated by some means; possibly by an earlier encounter with another galaxy.[48][50] 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.[51] 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.[52] M87 is estimated to have at least 50 satellite galaxies, including NGC 4486B and NGC 4478.[53][54]

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".[55][56] 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[55][56] or photoionization in the inner region powered by the jet.[57]

Elliptical galaxies such as M87 are believed to form as the result of one or more mergers of smaller galaxies.[58] 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.[59] 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.[31][60]


Supermassive black hole[edit]

Supermassive black holes are surrounded by massive accretion disks and generate jets of plasma
Artist's concept of a supermassive black hole and its accretion disk

The core contains a supermassive black hole that weighs billions of times the Sun's mass: estimates have ranged from (3.5 ± 0.8) × 109 M[61] to (6.6 ± 0.4) × 109 M,[61] with the latest measurement being 7.22+0.34
M.[62] This mass is one of the highest known 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,[63] and spans a maximum diameter of 0.12 parsecs (0.39 light-years).[64] Gas accretes onto the black hole at an estimated rate of one solar mass every ten years (about 90 earth masses per day).[65]

Observation suggests that the black hole may be displaced from the galactic center by about 7 parsecs (23 light-years).[66] The displacement is in the opposite direction of the one-sided jet, which may indicate that the black hole was accelerated away by the jet. Another possibility is that the change in location occurred during the merger of two supermassive black holes.[66][67] A 2011 study did not find any statistically significant displacement.[68]

Interstellar medium[edit]

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.[69][70] 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.[69] 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.[70][71] Since oxygen is produced mainly by core-collapse supernovae, which occur during the early stages of galaxies and mostly in outer star-forming regions,[69][70][71] 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.[69] The contribution of elements from these sources was much lower than in the Milky Way.[69]

Selected elemental abundances in the M87 core[69]
(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.[72] 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.[73] This dust may be destroyed by the hostile environment or expelled from the galaxy.[74] The combined mass of dust in M87 is no more than 70,000 times the mass of the Sun.[73] By comparison, the Milky Way's dust equals about a hundred million (108) solar masses.[75]

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.[76] These filaments have an estimated mass of about 10,000 solar masses.[47][76] Surrounding the galaxy is an extended corona with hot, low-density gas.[77]

Globular clusters[edit]

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,[78] compared to 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.[79] Within a 4 kiloparsecs (13 thousand light-years) 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.[77] Clusters with low metallicity are somewhat larger than metal-rich clusters.[79] In 2014, HVGC-1, the first hypervelocity globular cluster, was discovered escaping from M87 at 2300 km/s. The escape of the cluster with such a high velocity may have been the result of a close encounter with, and subsequent gravitational kick from, a supermassive black hole binary.[80] If this interpretation is correct, the core of M87 would have two supermassive black holes, the result of an ancient collision between two galaxies which merged into a single giant galaxy.[81]

Almost a hundred ultra-compact dwarfs have been identified in M87. They resemble globular clusters but have a diameter of 10 parsecs (33 light-years) or more, much larger than the 3-parsec (10 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.[82]


M87 jet extends up to 5000 light years from the core.
This Hubble Space Telescope photograph shows the jet of matter ejected from M87 at nearly the speed of light, as it stretches 1.5 kpc (5 kly) from the galactic core.
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.
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 thousand 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 parsecs (2.6 light-years) of the core, to about 16° at 2 parsecs (6.5 light-years), and to 6–7° at 12 parsecs (39 light-years).[83] Its base has the diameter of 5.5 ± 0.4 Schwarzschild radii, and is probably powered by a prograde accretion disk around a spinning supermassive black hole.[83] 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[84] (5.1 × 1049 joules or 3.2 × 1068 eV). This is roughly 1013 times the energy produced by the Milky Way in one second, which is estimated at 5 × 1036 joules.[85] 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.[86][87] The jet is precessing, causing the outflow to form a helical pattern out to 1.6 parsecs (5.2 light-years).[64] Lobes of expelled matter extend out to 80 kiloparsecs (260 thousand light-years).[88]

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.[89][90] It is proposed that M87 is a BL Lacertae object (with a low-luminosity nucleus compared with the brightness of its host galaxy) seen from a relatively large angle. Flux variations, characteristic of the BL Lacertae objects, have been observed in M87.[91][92]

M87 black hole is a strong source of radio waves
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 thousand light-years) in diameter around the black hole. Other features observed include narrow X-ray-emitting filaments up to 31 kiloparsecs (100 thousand 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. These observations also indicate that the variable eruptions produce sound waves of about 56 to 59 octaves below middle C in the medium.[93]

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.[94] In general, the smaller the diameter of the emission source, the faster the variation in flux, and vice versa.[94][95]

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,[96] while the X-ray emission has since been decaying in a variable manner.[97]

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.[98] 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 intracluster medium. At greater distances, both flows diffuse into two lobes. The lobes are surrounded by a fainter halo of radio-emitting gas.[99][100]


Visible wavelength image of Virgo cluster with M87 located near lower left
Messier 87 is a member of the Virgo Cluster, and can be seen to lower left of this cluster image.

M87 is near the center of the Virgo Cluster,[35] a closely compacted structure of about 2,000 members.[101] It forms the core of the larger Virgo Supercluster, of which the Local Group (including the Milky Way) is an outlying member.[48] It is organized into at least three distinct subsystems associated with the three large galaxies—M87, M49 and M86—with the subgroup centered around M87 (Virgo A) and M49 (Virgo B).[102] There is a preponderance of elliptical and S0 galaxies around M87, with a chain of elliptical galaxies aligned with the jet.[103] In terms of mass, M87 is a dominant member of the cluster, and hence appears to be moving very little relative to the cluster as a whole.[48] It is defined as the cluster center. The cluster has a sparse gaseous atmosphere that emits X-rays that decrease in temperature toward the middle, where M87 is located.[72] The combined mass of the cluster is estimated to be (0.15–1.5) × 1015 solar masses.[101]

Measurements of the motion of intracluster 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 in the past, 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 at the core of M87.[48]


  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.[6][7][8]
  2. ^ Epsilon Virginis is at celestial coordinates α=13h 02m, δ=+10° 57′; Denebola is at α=11h 49m, δ=+14° 34′. The midpoint of the pair is at α=12h 16m, δ=12° 45′. Compare to the coordinates of Messier 87: α=12h 31m, δ=+12° 23′.
  3. ^ This yields a distance of 16.4 ± 2.3 megaparsecs (53.5 ± 7.50 million light-years).[4]
  4. ^ This yields a distance of 16.7 ± 0.9 megaparsecs (54.5 ± 2.94 million light-years).[4]


  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 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 0-521-62556-4. 
  3. ^ a b c d e f "Results for NGC 4486". NASA/IPAC Extragalactic Database. California Institute of Technology. Retrieved 21 March 2018.  In "Source List", click "Row no. 1" OR click "Home", Select the "By Name" cell, then enter "NGC 4486" in the "Object Name:" field of the query form.
  4. ^ 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: 1–9. arXiv:1009.3202Freely accessible. Bibcode:2010A&A...524A..71B. doi:10.1051/0004-6361/201014876. 
  5. ^ 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. 
  6. ^ "The Local Universe". International Astronomical Union Division H. University of Leiden. Retrieved 1 May 2018. 
  7. ^ Courtois, H. M.; Pomarède, D.; Tully, R. B.; et al. (August 2013). "Cosmography of the Local Universe". The Astronomical Journal. 146 (3): 1–14. arXiv:1306.0091Freely accessible. Bibcode:2013AJ....146...69C. doi:10.1088/0004-6256/146/3/69. 
  8. ^ "Local Universe". Department of Astronomy, University of Wisconsin-Madison. University of Wisconsin-Madison. Retrieved 1 May 2018. 
  9. ^ 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. 
  10. ^ 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. 
  11. ^ 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. 
  12. ^ 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. 
  13. ^ Shklovskii, I. S. (August 1980). "Supernovae in Multiple Systems". Soviet Astronomy. 24: 387–389. Bibcode:1980SvA....24..387S. 
  14. ^ 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. 
  15. ^ Hubble, E. P. (December 1926). "Extragalactic nebulae". The Astrophysical Journal. 64: 321–369. Bibcode:1926ApJ....64..321H. doi:10.1086/143018. 
  16. ^ 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. 
  17. ^ Hubble, E. P. (1936). The realm of the nebulae. Mrs. Hepsa Ely Silliman Memorial Lectures, 25. New Haven: Yale University Press. ISBN 9780300025002. OCLC 611263346. Archived from the original on 5 September 2015. (pp. 16–17)
  18. ^ 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. 
  19. ^ 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. 
  20. ^ "Hubble follows spiral flow of black-hole-powered jet". ESA/Hubble Press Release. Archived from the original on 31 August 2013. Retrieved 6 September 2013. 
  21. ^ 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. 
  22. ^ 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. 
  23. ^ Charles, P. A.; Seward, F. D. (1995). Exploring the X-ray universe. Cambridge, United Kingdom: Cambridge University Press. p. 9. ISBN 0-521-43712-1. 
  24. ^ 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. 
  25. ^ 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. 
  26. ^ Sargent, W. L. W.; Young, P. J.; Lynds, C. R.; et al. (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. 
  27. ^ 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. 
  28. ^ 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 1-85233-901-2. 
  29. ^ Clark, R. N. (1990). Visual astronomy of the deep sky. Cambridge University Press. p. 153. ISBN 0-521-36155-9. 
  30. ^ "Visual observations of the M87 jet". Adventures in Deep Space. Astronomy-Mall. Archived from the original on 7 July 2011. Retrieved 7 December 2010. 
  31. ^ a b "Giant Galaxy is Still Growing". European Southern Observatory. 25 June 2015. Archived from the original on 25 June 2015. 
  32. ^ 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. 
  33. ^ Jones, M. H.; Lambourne, R. J. (2004). An introduction to galaxies and cosmology. Cambridge University Press. p. 69. ISBN 0-521-54623-0. 
  34. ^ Kundu, A.; Whitmore, B. C. (June 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/0103021Freely accessible. Bibcode:2001AJ....121.2950K. doi:10.1086/321073. 
  35. ^ a b Chakrabarty, D. (May 2007). "Mass modelling with minimum kinematic information". Monthly Notices of the Royal Astronomical Society. 377 (1): 30–40. arXiv:astro-ph/0702065Freely accessible. Bibcode:2007MNRAS.377...30C. doi:10.1111/j.1365-2966.2007.11583.x. 
  36. ^ 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. 
  37. ^ Whitmore, B. C. (15–17 May 1989). "Effect of the Cluster Environment on Galaxies". In William R. Oegerle; Michael J. Fitchett; Laura Danly. Clusters of galaxies: proceedings of the Clusters of Galaxies Meeting. Space Telescope Science Institute symposium series. 4. Baltimore: Cambridge University Press. p. 151. ISBN 0-521-38462-1. 
  38. ^ a b Wu, X.; Tremaine, S. (May 2006). "Deriving the Mass Distribution of M87 from Globular Clusters". The Astrophysical Journal. 643 (1): 210–221. arXiv:astro-ph/0508463Freely accessible. Bibcode:2006ApJ...643..210W. doi:10.1086/501515. 
  39. ^ 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/9704051Freely accessible. Bibcode:1997ApJ...486..230C. doi:10.1086/304518. 
  40. ^ 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): 1–21. arXiv:1101.1957Freely accessible. Bibcode:2011ApJ...729..129M. doi:10.1088/0004-637X/729/2/129. 
  41. ^ 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. 
  42. ^ Battaglia, G.; Helmi, A.; Morrison, H.; 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/0506102Freely accessible. Bibcode:2005MNRAS.364..433B. doi:10.1111/j.1365-2966.2005.09367.x. 
  43. ^ Gebhardt, K.; Thomas, J. (August 2009). "The Black Hole Mass, Stellar Mass-to-Light Ratio, and Dark Halo in M87". The Astrophysical Journal. 700 (2): 1690–1701. arXiv:0906.1492Freely accessible. Bibcode:2009ApJ...700.1690G. doi:10.1088/0004-637X/700/2/1690. 
  44. ^ Leverington, D. (2000). New cosmic horizons: space astronomy from the V2 to the Hubble Space Telescope. Cambridge University Press. p. 343. ISBN 0-521-65833-0. 
  45. ^ "Galactic Chromodynamics". ESO Picture of the Week. Retrieved 14 October 2014. 
  46. ^ 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:1408.6844Freely accessible. Bibcode:2014MNRAS.445L..79E. doi:10.1093/mnrasl/slu140. 
  47. ^ 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: 1120–25. Bibcode:1981AJ.....86.1120B. doi:10.1086/112992. 
  48. ^ a b c d e Doherty, M.; Arnaboldi, M.; Das, P.; 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:0905.1958Freely accessible. Bibcode:2009A&A...502..771D. doi:10.1051/0004-6361/200811532. 
  49. ^ 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. 
  50. ^ 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. 
  51. ^ Janowiecki, S.; Mithos, J. C.; Harding, P.; et al. (June 2010). "Diffuse Tidal Structures in the Halos of Virgo Ellipticals". The Astrophysical Journal. 715 (2): 972–985. arXiv:1004.1473Freely accessible. Bibcode:2010ApJ...715..972J. doi:10.1088/0004-637X/715/2/972. 
  52. ^ Gavazzi, G.; Boselli, A.; Vílchez, J. M.; et al. (September 2000). "The filament of ionized gas in the outskirt of M87". Astronomy & Astrophysics. 361: 1–4. arXiv:astro-ph/0007323Freely accessible. Bibcode:2000A&A...361....1G. 
  53. ^ 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:1607.02477Freely accessible. Bibcode:2016MNRAS.462..298O. doi:10.1093/mnras/stw1574. 
  54. ^ Fischer, D.; Duerbeck, H. (1998). Hubble Revisited: New Images from the Discovery Machine. Copernicus New York. p. 73. ISBN 978-0387985510. 
  55. ^ 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. The Radio Galaxy Messier 87. Lecture Notes in Physics. 530. pp. 307–312. arXiv:astro-ph/9801037Freely accessible. Bibcode:1999LNP...530..307T. doi:10.1007/BFb0106442. ISBN 978-3-540-66209-9. 
  56. ^ 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. 
  57. ^ 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/0210391Freely accessible. Bibcode:2003ApJ...584..164S. doi:10.1086/345664. 
  58. ^ Dehnen, Walter (15–19 September 1997). "M 87 as a Galaxy". In Hermann-Josef Röser; Klaus Meisenheimer. The radio galaxy Messier 87: proceedings of a workshop. Ringberg Castle, Tegernsee, Germany: Springer. p. 31. arXiv:astro-ph/9802224Freely accessible. Bibcode:1999LNP...530...31D. doi:10.1007/BFb0106415. 
  59. ^ Steinicke, W.; Jakiel, R. (2007). Galaxies and how to observe them. Astronomers' observing guides. Springer. pp. 32–33. ISBN 1-85233-752-4. 
  60. ^ Longobardi, A.; Arnobaldi, 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:1504.04369Freely accessible. Bibcode:2015A&A...579L...3L. doi:10.1051/0004-6361/201526282. 
  61. ^ 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): 1–11. arXiv:1304.7273Freely accessible. Bibcode:2013ApJ...770...86W. doi:10.1088/0004-637X/770/2/86. 
  62. ^ 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: 421–439. arXiv:1601.01323Freely accessible. Bibcode:2016MNRAS.457..421O. doi:10.1093/mnras/stv2982. Archived from the original on 20 March 2018. 
  63. ^ Macchetto, F.; Marconi, A.; Axon, D. J.; et al. (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/9706252Freely accessible. Bibcode:1997ApJ...489..579M. doi:10.1086/304823. 
  64. ^ 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. 
  65. ^ Di Matteo, .; Allen, S. W.; Fabian, A. C.; et al. (January 2003). "Accretion onto the Supermassive Black Hole in M87". The Astrophysical Journal. 582 (1): 133–140. arXiv:astro-ph/0202238Freely accessible. Bibcode:2003ApJ...582..133D. doi:10.1086/344504. 
  66. ^ a b Batcheldor, D.; Robinson, A.; Axon, D. J.; et al. (July 2010). "A Displaced Supermassive Black Hole in M87". The Astrophysical Journal Letters. 717 (1): L6–L10. arXiv:1005.2173Freely accessible. Bibcode:2010ApJ...717L...6B. doi:10.1088/2041-8205/717/1/L6. 
  67. ^ Cowen, R. (9 June 2010). "Black hole shoved aside, along with 'central' dogma". ScienceNews. 177 (13): 9. Archived from the original on 28 May 2010. Retrieved 29 May 2010. 
  68. ^ 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:1101.1954Freely accessible. Bibcode:2011ApJ...729..119G. doi:10.1088/0004-637X/729/2/119. 
  69. ^ a b c d e f Werner, N.; Böhringer, H.; Kaastra, J. S.; et al. (November 2006). "XMM-Newton high-resolution spectroscopy reveals the chemical evolution of M87". Astronomy and Astrophysics. 459 (2): 353–360. arXiv:astro-ph/0608177Freely accessible. Bibcode:2006A&A...459..353W. doi:10.1051/0004-6361:20065678. 
  70. ^ a b c Werner, N.; Durret, F.; Ohashi, T.; et al. (February 2008). "Observations of metals in the intra-cluster medium". Space Science Reviews. 134 (1–4): 337–362. arXiv:0801.1052Freely accessible. Bibcode:2008SSRv..134..337W. doi:10.1007/s11214-008-9320-9. 
  71. ^ a b Finoguenov, A.; Matsushita, K.; Böhringer, H.; et al. (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/0110516Freely accessible. Bibcode:2002A&A...381...21F. doi:10.1051/0004-6361:20011477. 
  72. ^ a b Shi, Y.; Rieke, G. H.; Hines, D. C.; et al. (February 2007). "Thermal and Nonthermal Infrared Emission from M87". The Astrophysical Journal. 655 (2): 781–789. arXiv:astro-ph/0610494Freely accessible. Bibcode:2007ApJ...655..781S. doi:10.1086/510188. 
  73. ^ a b Baes, M.; et al. (July 2010). "The Herschel Virgo Cluster Survey. VI. The far-infrared view of M87". Astronomy and Astrophysics. 518: 1–4. arXiv:1005.3059Freely accessible. Bibcode:2010A&A...518L..53B. doi:10.1051/0004-6361/201014555. 
  74. ^ 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: 1–4. arXiv:1005.3056Freely accessible. Bibcode:2010A&A...518L..50C. doi:10.1051/0004-6361/201014533. 
  75. ^ Jones, M. H.; Lambourne, R. J.; Adams, D. J. (2004). An introduction to galaxies and cosmology. Cambridge University Press. p. 13. ISBN 0-521-54623-0. 
  76. ^ 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. 
  77. ^ 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/9801214Freely accessible. Bibcode:1998AJ....115.1801H. doi:10.1086/300322.  The authors give a metallicity of:
    within a 3-kiloparsec radius of the galactic core.
  78. ^ Tamura, N.; Sharples, R. M.; Arimoto, N.; et al. (December 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/0609067Freely accessible. Bibcode:2006MNRAS.373..588T. doi:10.1111/j.1365-2966.2006.11067.x. 
  79. ^ a b Madrid, J. P.; Harris, W. E.; Blakeslee, J. P.; Gómez, M. (September 2009). "Structural Parameters of the Messier 87 Globular Clusters". The Astrophysical Journal. 705 (1): 237–244. arXiv:0909.0272Freely accessible. Bibcode:2009ApJ...705..237M. doi:10.1088/0004-637X/705/1/237.  See Fig. 6. for a plot of the effective cluster radius versus galactocentric distance.
  80. ^ Caldwell, N.; Strader, J.; Romanowsky, A. J.; et al. (May 2014). "A Globular Cluster Toward M87 with a Radial Velocity < -1000 km/s: The First Hypervelocity Cluster". The Astrophysical Journal Letters. 787: L11–L15. arXiv:1402.6319Freely accessible. Bibcode:2014ApJ...787L..11C. doi:10.1088/2041-8205/787/1/L11 (inactive 20 March 2018). 
  81. ^ Aguilar, D. A.; et al. "Entire Star Cluster Thrown Out of its Galaxy". Harvard-Smithsonian Center for Astrophysics. Archived from the original on 30 April 2014. 
  82. ^ Zhang, H.X.; Peng, E. W.; Côté, P.; 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): 1–26. arXiv:1501.03167Freely accessible. Bibcode:2015ApJ...802...30Z. doi:10.1088/0004-637X/802/1/30. 30. 
  83. ^ a b Doeleman, S. S.; Fish, V. L.; Schenck, D. E.; et al. (October 2012). "Jet-Launching Structure Resolved Near the Supermassive Black Hole in M87". Science. 338 (6105): 355–358. arXiv:1210.6132Freely accessible. Bibcode:2012Sci...338..355D. doi:10.1126/science.1224768. 
  84. ^ Baldwin, J. E.; Smith, F. G. (August 1956). "Radio emission from the extragalactic nebula M87". The Observatory. 76: 141–144. Bibcode:1956Obs....76..141B. 
  85. ^ 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. 
  86. ^ 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:0708.2695Freely accessible. Bibcode:2007ApJ...668L..27K. doi:10.1086/522603. 
  87. ^ 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. 
  88. ^ Klein, Uli (15–19 September 1997). "The Large-Scale Structure of Virgo A". In Hermann-Josef Röser; Klaus Meisenheimer. The radio galaxy Messier 87. Lecture Notes in Physics. 530. Ringberg Castle, Tegernsee, Germany: Springer. Bibcode:1999LNP...530...56K. doi:10.1007/BFb0106418. 
  89. ^ 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. 
  90. ^ Biretta, J. (6 January 1999). "Hubble detects faster-than-light motion in Galaxy M87". Baltimore, Maryland: Space Telescope Science Institute. Retrieved 21 March 2018. 
  91. ^ Tsvetanov, Z. I.; Hartig, G. F.; Ford, H. C.; et al. (February 1998). "M87: A Misaligned BL Lacertae Object?". The Astrophysical Journal. 493 (2): L83–L86. arXiv:astro-ph/9711241Freely accessible. Bibcode:1998ApJ...493L..83T. doi:10.1086/311139. 
  92. ^ 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. 
  93. ^ Roy, S.; Watzke, M. (October 2006). "Chandra Reviews Black Hole Musical: Epic But Off-Key". Chandra. Harvard-Smithsonian Center for Astrophysics. Archived from the original on 4 July 2010. Retrieved 25 April 2010. 
  94. ^ 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. 
  95. ^ Peterson, B. M. (26–30 June 2000). "Variability of Active Galactic Nuclei". In Aretxaga, I.; Kunth, D.; Mújica, R. Advanced Lectures on the Starburst-AGN Connection. Tonantzintla, Mexico: World Scientific. p. 3–68. arXiv:astro-ph/0109495Freely accessible. Bibcode:2001sac..conf....3P. doi:10.1142/9789812811318_0002. ISBN 978-981-02-4616-7. 
  96. ^ Harris, D. E.; Cheung, C. C.; Biretta, J. A.; et al. (March 2006). "The Outburst of HST-1 in the M87 Jet". The Astrophysical Journal. 640 (1): 211–218. arXiv:astro-ph/0511755Freely accessible. Bibcode:2006ApJ...640..211H. doi:10.1086/500081. 
  97. ^ Harris, D. E.; Cheung, C. C.; Stawarz, L. (July 2009). "Variability Timescales 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: 305–314. arXiv:0904.3925Freely accessible. Bibcode:2009ApJ...699..305H. doi:10.1088/0004-637X/699/1/305. 
  98. ^ Schneider, P. (2006). Extragalactic Astronomy and Cosmology: An Introduction (1st ed.). Heidelberg, Germany: Springer-Verlag. p. 178. ISBN 978-3-642-06971-0. 
  99. ^ 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/0006150Freely accessible. Bibcode:2000ApJ...543..611O. doi:10.1086/317151. 
  100. ^ "M87–Giant Elliptical Galaxy". Cool Cosmos. Caltech. Retrieved March 22, 2018. 
  101. ^ 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/0404138Freely accessible. Bibcode:2004ApJS..153..223C. doi:10.1086/421490. 
  102. ^ "Virgo Cluster". NASA-IPAC Extragalactic Database (NED). Archived from the original on 10 November 2013. Retrieved 25 December 2012. 
  103. ^ 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. 

External links[edit]

Coordinates: Sky map 12h 30m 49.4s, +12° 23′ 28″