M87 is a giant elliptical galaxy near the center of the Virgo cluster of galaxies, some 16 Mpc distant. M87 is also known as NGC4486, 3C274, and as Virgo A (the strongest radio source 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.
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M87 contains the nearest active galactic nucleus (AGN) in the northern sky, offering the possibility of studying an AGN at the highest linear resolution. The false-color image above was made with the "World Array" of radio telescopes at a wavelength of 18 cm. The image covers about 100 milli-arcseconds (mas) of sky with a resolution of about 4 mas. The center of the AGN is the bright spot on the left side of the image and the jet appears one-sided, heading off toward the upper right. One-sided AGN jets are probably caused by strong beaming of the emission for the side of the jet headed toward the observer. The jet is clearly resolved the jet across its width, and it shows quasi-helical structures and limb brightening. The wiggles can be caused by precession of the jet or by magneto-hydro-dynamic instabilities as the jet interacts with surrounding material in the AGN. The jet in M87 it thought to be powered by a super-massive black hole, which contains about 3 billion solar masses!
(Reference: Reid et al. 1989, ApJ, 336, 112)
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The image to the left is the first Space VLBI image of M87.
(It has been artifically rotated to make the jet appear horizontal.)
It has about four times better angular resolution
than the "World Array" image shown above.
Space VLBI uses a radio telescope in space
in conjunction with telescopes on the ground to achieve
interferometer baselines longer than an Earth's diameter.
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.
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