Intense Radio Sources Research Articles

A Radio Survey of the Great Loop in Cygnus

DURING the past few years, intense radio sources have been identified with galactic nebulosities in Taurus1 (the Crab Nebula), Cassiopeia2, Puppis3, Gemini4 (I.C.443) and Auriga5. One of these five objects (I.C.443) bears a marked resemblance to the Great Loop in Cygnus, and it has been suggested4 that the latter may also be a radio source. The Loop comprises the well-known Network nebulae N.G.C. 6960 and N.G.C.6992–5, together with several other patches of nebulosity. A rough sketch of the brighter parts of the system is shown in Fig. 1.

Radio Emission from the Perseus Cluster

A RADIO source the position of which coincides closely with the cluster of extragalactic nebulae in the constellation of Perseus has been observed by Ryle, Smith and Elsmore1, by Mills2 and by Hanbury Brown and Hazard3. The last-named authors have suggested that the observed radio emission is to be associated with the cluster as a whole, and they have pointed out that on this hypothesis there is an important discrepancy between the average radio emission of the individual galaxies of the cluster and that of nearby galaxies. Baade and Minkowski4, on the other hand, have suggested that the radio source should be identified with NGC 1275, one of the members of the cluster. This nebula, like that associated with the intense radio source in Cygnus, is probably another example of two galaxies in collision; the optical spectrum contains lines of high excitation and the structure suggests that a collision has taken place between an elliptical and a spiral nebula.

Position and Identification of a Bright Extended Radio Source in Gemini

OBSERVATIONS made at Cambridge with a new interferometric radio telescope1 working on a wavelength of 3.7 m. have shown the existence of an intense radio source of large diameter in the constellation of Gemini. This source (06.01) had been detected in a previous survey2 with an interferometric arrangement; but it had not been possible to determine its position accurately, partly because the resolving power was too great to give a good response with a source of this size and partly because the gain of the aerial was too small. In the present investigation, observations were made with a number of different resolving powers, and it was possible to determine both the position of the source and the distribution of brightness across it.

Cosmic Origin of Radiation at Radio Frequencies

THE recent identification by W. Baade and R. Minkowski of the intense discrete radio source in Cygnus as being an emission from two colliding galaxies1 raises a number of interesting theoretical questions. In the first place, the only material likely to be seriously disturbed by such a collision is the diffuse interstellar material lying between the stars in these galaxies. Consequently, it would seem profitable to seek a process of generation of radio waves that takes place in extremely diffuse gas clouds. Secondly, processes of magnetic resonance requiring field intensities of many gauss, such as the Larmor precession, would seem to be excluded, since fields of this intensity could scarcely be maintained throughout regions of galactic dimensions.