M 87

The giant elliptical galaxy M87, also called Virgo A, is one of the most remarkable objects in the sky. It is perhaps the dominant galaxy in the closest big cluster to us, the famous Virgo Cluster of galaxies (sometimes also called "Coma-Virgo cluster" which is more acurate, as it extends into constellation Coma), and lies at the distance of this cluster (about 60 million light-years).

M87's diameter of apparently about 7' corresponds to a linear extension of 120,000 light years, more than the diameter of our Milky Way's disk. However, as M87 is of type E1 (some sources give E0), it fills a much larger volume, and thus contains much more stars (and mass) than our galaxy, certainly several trillion solar masses (J.C. Brandt and R.G. Roosen have estimated 2.7 trillion). It is also of extreme luminosity, with an absolute magnitude of about -22.

M87 is famous for two peculiar and perhaps unique features, a huge globular cluster system found on long exposures, and a spectacular jet which is better seen on short exposure photographs.

This magnificient galaxy is perhaps the one with most known globular clusters. Several thousands (anyway more than 4,000) orbit this galaxy to form a conspicuous halo. The many satellite globular clusters of M87 can be viewed in this image.

The giant jet was discovered by H.D. Curtis of the Lick Observatory in 1918. This phenomenon extends thousands of light years (sources give 5,000, but maybe it is more as they are often based on too small distances of this galaxy; the present author would estimate 7-8,000 might be more likely). The jet is consisted of ejected gaseous material from the core of the galaxy. The light from the jet is mainly strongly polarized synchrotron radiation, as can be seen from its continuous spectrum, and it appears blue in (short exposure) color photos (as the one in J.D. Wray's Color Atlas of Galaxies). It is in violent turbulence; observations have shown apparent superluminal motion of gas clouds in this object - probably an illusion caused by the fact that the jet is pointing towards us.

Gorgeous detail of the Jet of M87 can be seen in this HST image which was processed by R. Mark Elowitz. Obviously it can be resolved into a string of small knots and clouds, a fact which was discovered in 1977 by H.C. Arp of Mt. Palomar and J. Lorre of JPL (according to Burnham). Earlier, in 1966, Arp had discovered a second jet, pointing to the opposite direction, which is significantly less conspicuous.

M87 was also identified with the strong radio source Virgo A (for the brightest radio source in the constellation Virgo), by W. Baade and R. Minkowski in 1954. In 1956, a weaker radio halo was found by J.E. Baldwin and F.G. Smith of Cambridge. It was also identified as a strong source of X-rays, and sits near the center of a hot X-ray emitting cloud extending far over the Virgo cluster.

It is on hand that such an interesting objects as M87 is under intensive investigation with the Hubble Space Telescope. In the Hubble Space Telescope views of M87, the violent active nucleus of this galaxy could be glimpsed significantly closer, to reveal a massive dark object of about 2-3 billion solar masses, concentrated within the innermost sphere with a radius of 60 light years. This object is surrounded by a rapidly rotating gaseous accretion disk. The gas may be part of a more extended system of interstellar matter, whioch was detected by Fabry-Perot interferometry by astronomers from the Calar Alto observatory around 1990.

The only supernova recorded for M87 appeared in February 1919, but was not detected before 1922 on photographic plates, by I. Balanowski, who estimated its maximum brightness as 11.5. At M87's distance, this corresponds to an absolute magnitude of nearly -20 mag.

Right ascension	12 : 28.3 (hours : minutes)
Declination	+12 : 40 (degrees : minutes)
Distance	70000.0 (light-years*10^3)
Visual magnitude	9.2