Messier Index/M87

Messier 87 (also known as M87, Virgo A or NGC 4486) is a giant elliptical galaxy. The galaxy is the largest and brightest galaxy within the northern Virgo Cluster, located about 55 million light years away. The galaxy also contains a notable active galactic nucleus that is a strong source of multiwavelength radiation, particularly radio waves. Since this is the largest giant elliptical galaxy near Earth and since it is one of the brightest radio sources in the sky, it is a popular target for both amateur astronomy observations and professional astronomy study. M87 is estimated to have a mass, within 32 kpc of its center, of 2.4 ± 0.6 M☉. Messier 87's diameter is a 120,000 light-years.

Globular clusters
M87 has an unusually huge population (perhaps the greatest known around any one galaxy) of globular clusters as compared to the Milky Way's 150-200. A 2006 survey out to 25&prime; of its core estimates that there are 12,000 ± 800 globulars around M87.

Jet
In 1918, Lick Observatory astronomer Heber Curtis discovered a jet of matter coming from M87 which he described as "a curious straight ray." This jet extends at least 5000 light-years from the nucleus of M87 and is made up of matter ejected from the galaxy, most likely by a supermassive black hole (a hypothesis made more likely by the discovery of a disk of rapidly rotating gas around the nucleus of M87). Astronomers believe that the black hole in this galaxy has a mass of approximately 6.4 billion (6.4&times;109) solar masses. M87 has also been found to be a strong source of X-rays. Its proximity means that it is one of the best studied radio galaxies.

Superluminal motion
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 motion is believed to be a visual result of the relativistic velocity of the jet, and not true superluminal motion. However, detection of such motion supports the theory that quasars, BL Lac objects and radio galaxies may all be the same phenomenon, known as active galaxies, viewed from different perspectives.

X-ray emitting loops and rings
Observations made by Chandra X-ray Observatory indicate the presence of loops and rings in the hot X-ray emitting gas that permeate the cluster and surround M87. These loops and rings are generated by pressure waves. The pressure waves are caused by variations in the rate at which material is ejected from the supermassive black hole in jets. The distribution of loops suggests that minor eruptions occur every six million years. One of the rings, caused by a major eruption, is a shock wave 85,000 light-years in diameter around the black hole. Other remarkable features observed include narrow X-ray emitting filaments up to 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. The observations also imply the presence of sound waves: 56 octaves below middle C for the minor eruptions and 58 to 59 below middle C for the major eruptions.

Gamma ray emissions
M87 is also a very strong source of gamma rays, which are the most energetic rays of the electromagnetic spectrum; more than a million times as powerful as visible light. Gamma rays coming from M87 have been observed since the late 1990s, but recently, using the HESS Cherenkov telescopes, scientists have measured the variations of the gamma ray flux coming from M87, and found that the flux changes over a matter of days.

It is generally accepted that the supermassive black hole located in the center of M87 holds a mass of several billion solar masses. However, the fact that the variations can change over several days makes the immediate vicinity of the supermassive black hole in M87 (about the size of our solar system) the most promising source of the gamma rays. In general, the smaller the diameter, the faster the variations, and vice versa.