Messier 87 - Jet

Jet

In this Chandra X-ray Observatory image, cold matter from the Virgo cluster falls toward the core of M87, where it's met by the relativistic jet, producing shock waves in the galaxy's interstellar medium.

The relativistic jet of matter emerging from the core extends at least 1.5 kpc (5 kly) from the nucleus of Messier 87 and is made up of matter ejected from the galaxy by a supermassive black hole. This jet is highly collimated, appearing constrained to an angle of about 16° within 2 pc (6.5 ly) of the core and an angle of 6–7° at a distance of 12 pc (39 ly). It is surrounded by a lower velocity, non-relativistic component. There is evidence of a counter jet, but this feature remains unseen from the Earth due to relativistic beaming. The jet is precessing, causing the outflow to form a helical pattern out to a distance of 1.6 pc (5.2 ly). Lobes of matter from the jet extend out to a distance of 77 kpc (250 kly).

In pictures taken by the Hubble Space Telescope in 1999, the motion of Messier 87's jet was measured at four to six times the speed of light. This motion may be an optical illusion caused by 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.

Observations made by Chandra X-ray Observatory indicate the presence of loops and rings in the hot X-ray emitting gas that permeates the cluster and surrounds Messier 87. 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 26 kpc (85 kly) in diameter around the black hole. Other features observed include narrow X-ray emitting filaments up to 31 kpc (100 kly) 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.

Messier 87 is a very strong source of gamma rays, which are the most energetic rays of the electromagnetic spectrum. Gamma rays coming from Messier 87 have been observed since the late 1990s, but in 2006, using the HESS Cherenkov telescopes, scientists have measured the variations of the gamma ray flux coming from Messier 87, and found that the flux changes over a matter of days. This short period makes the immediate vicinity of the supermassive black hole in Messier 87 the most promising source for these gamma rays. In general, the smaller the diameter of the emission source, the faster the variation in flux, and vice versa.

A knot of matter in the jet, designated HST-1, has been tracked by the Hubble Space Telescope and the Chandra X-ray Observatory. This knot is about 65 pc (210 ly) from the core. By 2006, the X-ray intensity of this knot had increased by a factor of 50 over a four year period. This X-ray emission has since been decaying in a variable manner.