Graphic courtesy: Shep Doeleman MIT
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Astronomers linked together the radio telescopes shown above to create a 'virtual' telescope whose size is equal to the distance between sites in Hawaii and those in Arizona and California. The ability of this new telescope to see fine details (1,000 times better than the Hubble Space Telescope) allowed an international team to measure the size of the super-massive black hole (shown as an artist's conception) in the center of the Milky Way.

Graphic courtesy: Shep Doeleman/MIT, M. Weiss/NASA/CXC, S. Noble/Johns Hopkins,
C. Gammie/U.Illinois
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This illustration shows the extreme activity astronomers believe occurs near a super massive black hole. Matter that is spiraling inward forms a disk swirling around the black hole, and high speed jets of energetic particles are ejected from the North and South poles of the black hole.
The inset detail shows a computer simulation of matter orbiting just outside the black hole. The rotation of the disk surrounding the black hole causes the side moving towards us (in this case the left side) to brighten. The size of this bright spot in the rotating disk is close to the size measured with the new observations.