Jet-triggered Type Ia supernovae in radio galaxies?

We report the serendipitous discovery of a supernova (SN) in the nearby radio galaxy 3C 78. Observations obtained with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope show, at a distance of 0."54 (300 pc) from the galaxy nucleus, a second bright source, not present in previous images. As this source was fortuitously covered by the spectrograph slit, its spectrum was obtained, and it is characteristic of a Type Ia SN. This SN is closely aligned with the radio jet of 3C 78. Analysis of historical records shows that such a close association between jet and SN occurred in six of the 14 reported SNe in radio galaxies. The probability that this results from a random distribution of SNe in the host galaxy is less than similar to0.05%. We then argue that jets might trigger SN explosions.