Elliptical galaxy M87
The elliptical galaxy M87 (also known as Virgo A Galaxy, Virgo A, Messier 87, M87, or NGC 4486) is a giant elliptical galaxy easy to see with amateur telescopes. It is the largest and most luminous galaxy in the northern zone of the Virgo Cluster, and is located in the center of the Virgo A subgroup (the most massive of all the subgroups into which the cluster is divided).). The galaxy also contains a notable active galactic nucleus, which is a high-intensity source of broad-wavelength radiation, particularly at radio frequencies, and an energetic plasma jet originating from the nucleus and extending at least 1,500 parsecs (4,900 light-years), and travel at a relativistic speed. As it is the brightest near-Earth elliptical galaxy and one of the brightest radio sources in the sky, it is a popular target for both amateur and astronomical astronomy. for scientific study. The galaxy is estimated to have a mass within a 32 kpc radius of 2.6 ± 0.3 × 1012 solar masses, twice the mass of our galaxy, and including dark matter may be 200 times more massive than this. M87 is about 16.4 million parsecs (53 million light-years) from Earth.
Globular clusters and outer halo
M87 has an unusually large population of globular clusters. In a 2006 survey, it was estimated that there were about 12,000 ± 800 clusters around M87, compared to 150-200 for the Milky Way.
In addition, it is surrounded by a large halo only visible in very long exposure and sensitivity photographs, very elongated and irregular in shape and extending at least 30 minutes of arc (the apparent size of the full Moon) -corresponding to a real size of more than half a million light years at the distance of this galaxy-, and which is believed to be formed by stars belonging to galaxies that have been destroyed by the gravitational attraction of M87 in close encounters with it, to later be finally absorbed. This halo appears to be distorted by the gravitational pull of neighboring galaxies in the Virgo cluster, and its presence explains why M87 is sometimes classified as a cD-type galaxy, albeit an incipient one.
The halo appears to extend to a distance of about 150 kiloparsecs; the reason why it ends at that distance is unknown, and the possibilities considered include a past encounter between M87 and another galaxy - surely M84 - or a contraction of this one due to dark matter falling towards the galaxy treated here; the same study in which this has been suggested also proposes that M87 and M86 are falling towards each other and that they are being observed just before their first close approach. In it, there are also various streams of stars, and it is believed that they have been ripped from other nearby galaxies or that they are remnants of smaller galaxies destroyed and absorbed by M87.
Jet of matter and interstellar medium
In 1918, astronomer Herber Curtis of Lick Observatory discovered a jet of matter coming from M87, which he described as "a curious straight ray". This jet of matter or jet extends at least 5000 light-years from the core of M87, and is made up of matter ejected from the galaxy itself, probably from a supermassive black hole located at its center. Astronomers believed that the black hole in this galaxy has a mass of about 3.2 billion solar masses, but recent research pushes that mass up to between 6.4 and 6.6 billion solar masses. This black hole is surrounded by a disk of gas hot, which feeds it at the rate of one solar mass every 10 years, and it has been suggested that its position does not coincide with that of the exact center of this galaxy, and is approximately 22 light years from it (something whose causes are unknown and that It has been attributed to the fact that M87 was born after the merger of two previous galaxies with supermassive black holes at its center and that, when these merged, it would have ended up there, or also that the jet would have propelled the black hole to that distance).
On August 22, 2013, a study was published based on observations made, from 1995 to 2008, by various specialists in the deep Universe, taking advantage of the possibilities of the Hubble Space Telescope. They obtained a series of time-lapse movies showing a 5,000-light-year-long jet of plasma being ejected from a supermassive black hole. That black hole seems to be located in the center of the galaxy M87. It seems that he found evidence that suggests the spiral movement of that jet, creating a helix-shaped magnetic field that surrounds the black hole. On the outside of the jet, a clump of glowing gas, which they called “knot B”, appears to zig-zag.
Other authors deny that such a shift exists. In M87, an intense X-ray source has also been found, and its proximity means it is one of the best-studied radio galaxies.
There is gas falling towards the galaxy at a rate of 2-3 solar masses per year, much of it ending up in the central region of the galaxy and at least in part appearing to come from a gas-rich minor galaxy that is being absorbed by M87.
The interstellar medium of this galaxy is occupied by a gas enriched in elements such as carbon and nitrogen, which have been produced mainly by stars existing in the giant asymptotic branch, and oxygen and iron produced by supernovae, especially type Ia. The abundance of these elements is half the abundance in the Sun up to a radius of 4 kiloparsecs, and increases beyond this radius.
Finally, M87 has various filaments of dust with masses of around 10,000 solar masses, and other filaments of hot gas that appear to come from the minor absorbing galaxy mentioned above, and is surrounded by a halo of hot gas.
Superluminal motion
In images taken by the Hubble Space Telescope in 1999, the motion of M87's jet of matter was measured and found to be four to six times the speed of light. This movement is the visual result of the relativistic velocity of the jet of matter, and not of a true superluminal movement. The detection of such motion supports the theory that quasars, BL Lacertae objects, and radio galaxies may be the same phenomenon, known as active galaxies, viewed from different perspectives; indeed, some astronomers have suggested that M87 may actually be a galaxy. of type BL Lacertae (although, unlike other objects of this class, with a nucleus of low brightness, compared to the rest of the galaxy) seen from an angle that is unfavorable to appreciate the properties of this type of objects.
X-ray emission loops and rings
Observations made by the Chandra space telescope indicate the presence of loops and rings in the hot, X-ray-emitting gas that spans the cluster and surrounds M87. These loops and rings are formed by pressure waves. The pressure waves are caused by variations in the speed at which matter is ejected from the supermassive black hole in jets. The distribution of the 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 notable features are fine filaments of X-ray emission, which extend to a length of 100,000 light-years, and a large cavity in the hot gas, caused by a large eruption 70 million years ago.
Unlike in other giant elliptical galaxies at the center of galaxy clusters, such as NGC 6166, regular eruptions prevent the hot gas that fills the intergalactic medium of the Virgo Cluster from falling toward the center of this galaxy, so it cools and stars are formed, which implies that the evolution of M87 could have been greatly affected, preventing it from becoming a large spiral galaxy. The observations also signified the presence of sound waves: 56 octaves below middle C for minor eruptions and 58 or 59 octaves below middle C for major ones.
Gamma Ray Emissions: Supermassive Black Hole
M87 is also a source of gamma rays. Gamma rays are the most energetic in the electromagnetic spectrum; more than a million times stronger than visible light. Gamma rays from M87 began to be observed in the late 1990s, but later, using HESS telescopes, scientists have measured the variation of the gamma-ray flux and found that the changes occur in a matter of days.
It has been accepted that at the center of M87 lies a supermassive black hole (it was proposed to call it Powehi, which is Hawaiian for "ornate and fathomless dark creation"), with a mass of several billion solar masses. However, the fact that the variations can change in a few days makes the immediate environment of the supermassive black hole of M87, with a size similar to the Solar System, the most promising location of gamma rays. In general, the smaller the surface, the faster the variation and vice versa.
The first image of the black hole, made public on Wednesday, April 10, 2019, was taken by the Event Horizon Telescope (EHT), an array of eight telescopes, thanks to an algorithm generated by a team at the Massachusetts Institute of Technology (MIT) Computer Science and Artificial Intelligence Laboratory, the Harvard-Smithsonian Center for Astrophysics, and the MIT Haystack Observatory, led in 2016 by Katie Bouman, who at the time was a graduate student at MIT itself.