A counterjet in the elliptical galaxy M87
Résumé
An optical counterpart to the radio hotspot in the southeast lobe of M87 has been identified at about the same distance as the radio jet but oppositely located. Polarization data identify the optical emission as synchrotron radiation, and the severe energetic requirements of maintaining this emission suggest continuous replenishment at the site of the hotspot. It is proposed that this is provided by an invisible 'counterjet', and it is argued that the counterjet cannot be identical to the visible known jet but must be intrinsically somewhat fainter.