Markarian 501
is more than 300 million light years distant from the earth. It has an
active nucleus, the source of energy for the jet of fast-moving
particles seen in this VLBA image. The image reveals a remarkable
feature in the jet - a dramatic twisting in direction through nearly a
right angle. VLBA images like this one help astronomers to understand
the nature of jets, active galactic nuclei, and the black holes they
may harbor.