At first glance, M87 (also known as NGC 4486) appears to be an ordinary giant elliptical galaxy; one of many ellipticals in the nearby Virgo cluster of galaxies. However, as early as 1918, astronomer H.D. Curtis noted a "curious straight ray" protruding from M87. In the 1950s when the field of radio was blossoming, one of the brightest radio sources in the sky, Virgo A, was discovered to be associated with M87 and its jet.
After decades of study, prompted by these discoveries, the source of this incredible amount of energy powering the jet has become clear. Lying at the center of M87 is a supermassive object, which has swallowed up a mass equivalent to 2 billion times the mass of our Sun. This object may be a supermassive Black Hole, according to what many astronomers currently think. The jet originates in the disk of superheated gas swirling around this object and is propelled and concentrated by the intense, twisted magnetic fields trapped within this plasma. The light that we see (and the radio emission) is produced by electrons twisting along magnetic field lines in the jet, a process known as synchrotron radiation, which gives the jet its bluish tint.
M87 is one of the nearest and is the most well-studied extragalactic jet, but many others exist. Wherever such a massive central object is feeding on a particularly rich diet of disrupted stars, gas, and dust, the conditions are right for the formation of a jet. Interestingly, a similar phenomenon occurs around young stars, though at much smaller scales and energies.
At a distance of 50 or 60 million light-years, M87 is too distant for Hubble to discern individual stars. The dozens of star-like points swarming about M87 are, instead, themselves clusters of hundreds of thousands of stars each. An estimated 15,000 globular clusters formed very early in the history of this galaxy and are older than the second generation of stars, which huddle closer to the center of the galaxy.
The data were collected with Hubble's Wide Field Planetary Camera 2 in 1998 by J.A. Biretta, W.B. Sparks, F.D. Macchetto, and E.S. Perlman (STScI). The Hubble Heritage team combined these exposures of ultraviolet, blue, green, and infrared light in order to create this color image.
Credit: NASA and The Hubble Heritage Team (STScI/AURA)
Last Modification: 2 Sep 2001, 10:30 MET