BL Lac Object OJ287

Six epochs of observations of the BL Lac object, OJ287. We see a bright core and jet extending to the west (left). The black dots indicate the approximate positions of the "core" and a bright "knot" of plasma traveling outward in the jet. The "knot" appears to move at nearly 20 times the speed of light! The illusion of faster-than-light motion is common in radio jets like this one, and these images are from a monitoring program made with the VLBA during 1996.

Credit: D.C. Homan, R. Ojha, J.F.C. Wardle, D.H. Roberts (Brandeis) and M.F. Aller, H.D. Aller, P.A. Hughes (Univ Michigan) 2002, Astrophys. Journal, vol 549, page 840