1999AJ....117.1143O

We present Hubble Space Telescope Wide Field Planetary Camera 2 broadband red and linear ramp filter (isolating redshifted [O II] λ3727) observations and subarcsecond-resolution 15, 22, and 43 GHz VLA observations of the radio-loud quasar 3C 380. We confirm the report of de Vries et al. that there is good correspondence between the locations of two optical and radio knots/hot spots in the jet. We show that the optical knots are continuum rather than line emission. The radio-optical spectrum can be fitted either by a normal radio spectrum (α~-0.8) with a break somewhere in the infrared or by a steeper single power law (α~-1) (where S_ν∝ν^α). We suggest that the two knots are radiating optical synchrotron emission. This would make the knots in 3C 380 the most luminous optical knots/hot spots currently known.