Active Galactic Nuclei

M87 is a giant elliptical galaxy near the center of the a large cluster of galaxies at a distance of 16 Mpc in the constellation Virgo. It is one of the first galaxies discovered to have an optical "jet", which is visible faintly as it protrudes through the bright optical emission from the stars in the galaxy. M87 contains the nearest active galactic nucleus (AGN) in the northern sky, offering the possibility of studying an AGN at the highest linear resolution. At radio wavelengths, AGN often display dramatic jets, with a bright spot at the nucleus and long-thin trails of emission emanating from the nucleus, passing through the entire galaxy, and ending in huge "radio lobes" well outside the galaxy. The jet in M87 it thought to be powered by a super-massive black hole, which contains about 3 billion solar masses!

The image shown on the right is the first Space VLBI image of M87. It used radio telescopes spread across the Earth and one in space to simulate a telecope with incredible angular resolution. The Japanese HALCA space craft carrying the VSOP telescope came into operation in 1997 and has well demonstrated the potential of Space VLBI. This image reveals that the jet remains strongly limb-brightened to within 2 mas of the black hole.