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Giant Elliptical Galaxy M87
The giant elliptical galaxy M87, also called Virgo A, is a remarkable object. It is the largest galaxy in the closest cluster of galaxies to us— the famous Virgo Cluster of galaxies—and lies at the distance of about 55 million light years. M87's diameter is120,000 light years, more than the diameter of our Milky Way's disk. However, because M87 is elliptical of type E1 or E0, it fills a much larger volume, and thus contains many more stars (and mass) than our galaxyabout 2.7 trillion solar masses. It is also of extreme luminosity, with an absolute magnitude of about 22.
M87 is famous for two peculiar features: a huge globular cluster system found on long exposures (as in this image), and a spectacular jet, which is better seen on short exposure photographs. This magnificient galaxy has the most known globular clusters. While our Milky Way has the modest number of roughly 150 to 200 globulars, M87 possesses a remarkable system of 4,000 to 15,000 surrounding this giant galaxy in a conspicuous halo.
The giant jet was discovered by H.D. Curtis of the Lick Observatory in 1918. This phenomenon extends 7,000 to 8,000 light years, consisting of gaseous material ejected from the core of the galaxy. Polarimetric exposures of this jet have shown that its light is strongly polarized in a way which is typical for synchrotron radiation. It exhibits a continuous spectrum, and appears blue in (short exposure) color photos. It is in violent turbulence; observations have shown apparent superluminal motion of gas clouds in this objectan illusion caused by the fact that the jet is pointing towards us.
M87 was also identified with the strong radio source "Virgo A."