The jet of the quasar 3C 273.

New observations of the jet in 3C 273 support and refine an earlier interpretation that (1) the mapped jet is 10 exp 6 + or - 0.3 yr old and grows at 0.6 to 0.75 times the speed of light, at an average angle theta of 20 + or - 10 deg with respect to the line of sight; (2) its twin is not seen yet because arriving signals were emitted when it was some 10 exp 6 + or - 0.2 times younger; (3) the fluid moving in the jet is an extremely relativistic electron-positron-pair plasma, of bulk Lorentz factor greater than approximately 100; (4) the beam has swung in projection through some 10 deg; and (5) the small excursions (wiggles) of the jet around its average propagation direction result from a self-stabilizing interaction with the nonstatic ambient plasma. All other interpretations considered depend heavily on the ('beaming') assumption that the jet material radiates isotropically in some (comoving) Lorentz frame, an assumption which is believed to be unrealistic.