In 1982, it was found that thenucleus of NGC 1218 emits aradio jet.[8] A follow-up study in 1986 corroborated the presence of the jet, as well as finding evidence of a possible weak counter-jet.[9] The Hubble Space Telescope observed NGC 1218 on August 17, 1994. An optical jet ofsynchrotron radiation similar to that ofMessier 87 was subsequently found.[10]
On September 6, 2000, atype Ia supernova was detected in NGC 1218. A 2002 study found that the previously identified radio jet was the cause.[11]
NGC 1218 is a lenticular (S/0a)radio galaxy, with a radiohalo roughly equivalent in size to the optical halo's extent.[8] The observable synchrotron jet has a total length of 1.37 arcseconds (0.75 kpc), and expands substantially at 0.5 arcseconds from the nucleus.[10]
NGC 1218 has an approximatehydrogen mass of <36×109M☉.[9]
3C 78 is an astronomical radio source with an angular extent of approximately 80 × 55 arcseconds squared.[9] According to Tabara and Inoue (1980), 3C 78 has arotation measure of 8.7 ± 1.9 m−2 and an intrinsicposition angle of 87° ± 4°, although Simard-Normandin, Kronberg, and Button (1981) claim that it has a rotation measure of 14 ± 2 m−2 and an intrinsic position angle of 85° ± 3°.[13][14]
It possesses a radio jet approximately one arcsecond (0.58 kpc) in length, with three bright, compact inhomogeneities (or "knots"), with the second and thirds ones being the most prominent. The second knot has a longitudinal motion of approximately 0.51 ± 0.14c at roughly 200 pc, and the third knot had an apparent superluminal backwards motion of −2.6 ± 2c prior to 2000, followed by a forward motion of 0.5 ± 2c, both at roughly 300 pc.[12]
