One of the largest and most massive galaxies in the local universe,[b] 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.

Instead, it has an almost featureless, ellipsoidal shape typical of most giant elliptical galaxies, diminishing in luminosity with distance from the center.

[13] 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.

[16] 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."

[27][28] 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.

[29] Subsequent X-ray observations by the HEAO 1 and Einstein Observatory showed a complex source that included the active galactic nucleus of M87.

[9] M87 has been an important testing ground for techniques that measure the masses of central supermassive black holes in galaxies.

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,[d] and the tip of the red-giant branch method using individually resolved red giant stars.

[55] 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.

[61][62] 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).

Possible causes include shock-induced excitation in the outer parts of the disk[63][64] or photoionization in the inner region powered by the jet.

[67] 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.

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.

[68][69] The core of the galaxy contains a supermassive black hole (SMBH), designated M87*,[34][71][13] whose mass is billions of times that of the Earth's Sun; estimates had ranged from (3.5±0.8)×109 M☉[72] to (6.6±0.4)×109 M☉,[72] surpassed by 7.22+0.34−0.40×109 M☉ in 2016.

[90] On 24 March 2021, the Event Horizon Telescope collaboration revealed an unprecedented unique view of the M87 black hole shadow: how it looks in polarized light.

[92] Knowing those is essential to understand how M87's supermassive black hole is launching jets of magnetized plasma, which expand at relativistic speeds beyond the M87 galaxy.

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

[clarification needed][93] In April 2023, a team developed a new principal-component interferometric modeling (PRIMO) technique to produce sharper image reconstructions from EHT data.

[96] 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.

[96] 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.

[102][103] 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.

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.

[106][107] 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.

[110] The interaction of relativistic jets of plasma emanating from the core with the surrounding medium gives rise to radio lobes in active galaxies.

Carbon and nitrogen are continuously supplied by stars of intermediate mass as they pass through the asymptotic giant branch.

Emission probably comes from shock-induced excitation as the falling gas streams encounter X-rays from the core region.

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,[123] compared with 150–200 in and around the Milky Way.

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.

[127] This forms the core of the larger Virgo Supercluster, of which the Local Group (including the Milky Way) is an outlying member.

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.