DO POWERFUL LARGE-SCALE JETS HAVE FAST SPINAL SPEEDS?
3.1. The impetus from PKS 0637-752 Chandra is central to the current debate concerning jet speed in the powerful radio jets of quasars. The work was kick-started unexpectedly. Observing quasars was not initialy a high scientific priority for Chandra, as it was recognized that the cores were bright, and the likelihood of multiple photons arriving between CCD readouts was high, leading to distorted spectral measurements (so called `pileup’). It was thus fortuitous that a radio-loud quasar was the chosen target for in-flight focus calibration, since this led to the detection of resolved jet emission from the z = 0.651 quasar PKS 0637-752 ([177, 45], and see Fig. 6).
