Messier 87

Messier 87
en:NASA, en:STScI, en:WikiSky · Public domain · source
Name	Messier 87
Caption	The relativistic jet emanating from the core of Messier 87, as imaged by the Hubble Space Telescope.
Epoch	J2000
Constellation	Virgo
Ra	12, 30, 49.4
Dec	+12, 23, 28
Dist ly	53.5 ± 1.6 Mly (16.4 ± 0.5 Mpc)
Type	E+0-1 pec, cD galaxy
Size v	7.2′ × 6.8′
Appmag v	+8.6
Notes	Hosts the first directly imaged black hole.

Messier 87 is a supergiant elliptical galaxy located in the constellation Virgo. It is a dominant member of the Virgo Cluster and is renowned for hosting a supermassive black hole at its core, which was the first to be directly imaged by the Event Horizon Telescope collaboration. The galaxy is also famous for its prominent relativistic jet of energetic plasma, a feature that has been extensively studied across the electromagnetic spectrum.

Discovery and observation

The galaxy was discovered in 1781 by the French astronomer Charles Messier, who catalogued it as the 87th entry in his famous list of non-cometary objects. Later observations by William Herschel and his son John Herschel noted its nebulous, star-like core. Detailed study advanced significantly in the 20th century with the advent of large telescopes, and it became a key target for Edwin Hubble's work on extragalactic astronomy. Modern observations utilize instruments like the Hubble Space Telescope, the Chandra X-ray Observatory, and the Very Large Array, which have revealed its complex structure and energetic phenomena.

Physical characteristics

Messier 87 is classified as a cD galaxy, a supergiant elliptical that sits at the dynamical center of its cluster. It has an estimated stellar mass of about 2.4 trillion times that of the Sun, significantly larger than that of the Milky Way. The galaxy exhibits a vast, diffuse halo of stars and a notable population of roughly 12,000 globular clusters, far exceeding the count in our own galaxy. Its optical appearance is smooth and featureless, characteristic of an old stellar population, but it is embedded in a massive halo of hot X-ray-emitting gas detected by observatories like ROSAT.

Supermassive black hole

At the heart of Messier 87 lies a supermassive black hole, designated M87*, with a mass equivalent to 6.5 billion solar masses. This object gained worldwide fame in 2019 when the Event Horizon Telescope project, a global network of radio observatories including the Atacama Large Millimeter Array and the South Pole Telescope, released the first-ever direct image of a black hole's event horizon and shadow. The dynamics of stars and gas close to the galactic center, studied by instruments like the Gemini Observatory, provided earlier compelling evidence for the black hole's immense gravitational influence.

Jet and relativistic beaming

One of the most striking features of Messier 87 is a powerful, collimated jet of plasma extending at least 5,000 light-years from its core. This jet is a result of material from the accretion disk around the black hole being accelerated to relativistic speeds. The phenomenon of relativistic beaming makes the jet appear brighter when pointing toward Earth, and it is a strong emitter from radio waves to gamma-rays. Studies by the Fermi Gamma-ray Space Telescope and the High Energy Stereoscopic System have shown the jet's variability and its role in accelerating particles to extreme energies.

Galactic environment

Messier 87 is the central dominant galaxy of the Virgo Cluster, the nearest large cluster of galaxies to the Local Group. Its gravitational influence is immense, as it is undergoing galactic cannibalism, absorbing smaller satellite galaxies, a process evidenced by observed stellar streams. The galaxy sits at the center of a vast reservoir of intracluster medium, with its activity influencing gas dynamics and star formation across the cluster. Its interaction with this environment makes it a crucial laboratory for studying active galactic nucleus feedback and the evolution of cosmic structures. Category:Elliptical galaxies Category:Virgo Cluster Category:Messier objects Category:Virgo (constellation)