170364a0Nature1704322195208303643650028-0836195210.1038/170364a0ukNatureNatureNATUREnatureNature is a weekly international journal publishing the finest peer-reviewed research in all fields of science and technology on the basis of its originality, importance, interdisciplinary interest, timeliness, accessibility, elegance and surprising conclusions. Nature also provides rapid, authoritative, insightful and arresting news and interpretation of topical and coming trends affecting science, scientists and the wider public./nature/journal/v170/n4322issueJournal homeArchiveCurrent issueAdvance online publicationPrivacy policySubscribeNature Publishing GroupCurrent issue170364a0Radio-Frequency Radiation from Tycho Brahe's Supernova (A.D. 1572)
AU  - HANBURY BROWN, R.
AU  - HAZARD, C.Jodrell Bank Experimental Station, Holmes Chapel, Cheshire. July 14.SINCE the discovery of localized sources of extraterrestrial radio-frequency radiation in 19481, surveys have been carried out over the whole sky2,3, and the positions and intensities of about one hundred sources are now known. Although a few of these sources have been identified with extra-galactic nebulae3-5 it is generally considered that the majority must lie within the Galaxy with a distribution, and perhaps a density, similar to that of the common visual stars6. However, it has not yet been possible to associate the radio sources with any class of visual objects in the Galaxy, and in only one instance has an identification been made, namely, the identification of a source in Taurus with the Crab nebula7. As the Crab nebula is believed to be the remnant of the supernova of 1054, it is to be expected that the remnants of other supernovae are also sources of radio radiation. The other supernovae known to have occurred in the Galaxy are those of 1572 and 1604, but the published surveys show no radio source in either of these positions.Recently, a detailed survey8 has been made of that region of the sky which lies within the field of view of the 218-ft. paraboloid at the Jodrell Bank Experimental Station. The observations have been made at 158-5 Mc./s., and at this frequency the aerial has a beam-width of 2  between half-power points. In this survey a number of localized sources of radiation have been detected, several of which have not been reported previously. The co-ordinates of one of these sources agree closely with those of the supernova of 1572, as shown in Table 1, and in view of this agreement the radio source may be tentatively identified with the remnant of the supernova.
Table 1. DATA ON RADIO SOURCE AND SUPERNOVA (1572) EPOCH 1950
R.A. Declination Intensity[ast]
Radio OOh. 23m. 49s. [plusmn]2m. N. 64 15' [plusmn]35' l-7xl(T24 source W./sq.m./cps. [plusmn]
25 per cent
Supernova OOh. 22m. 0-2s. N. 63  52' 12[ast] of 1572 (ref. 10)
[ast] The intensity given is twice that observed in one plane of polar-zation.
The chief difficulty in observing this source lies in its proximity to the intense source Cassiopeia I (R.A. 23h. 21m. 12s., decimation N. 58  32', Epoch 1950 3), and when it was first observed in 1951 there was some doubt as to whether it was genuine, or represented the reception of the nearby intense source in a side lobe of the aerial beam. This doubt has now been removed by means of a special interferometer which observed the two sources simultaneously, and showed that the radiation received from the source in the position of the supernova is incoherent with that received from Cassiopeia I. The proximity of this source to Cassiopeia I presumably explains why it was not reported in the survey made with an interferometer at 81 Mc./s. by Ryle, Smith and Elsmore3.
Table 2 shows a comparison between the visual data available for the supernovae of 1054 and 1572 and the intensities of the associated radio sources.
Table 2. COMPARISON or THE SUPERNOVA OF 1054 AND 1572
Supernova	Apparent visual magnitude at maximum brightness	Apparent integrated photographic magnitude of remnant	Intensity[ast] of associated radio source (watts/sq. m./cps.)
A.D. 1054 A.D. 1572	-6-5 to -7-0 (ref. 9) ~ -4-0	+ 9 (ref. 10) > +15 (ref. 11)	19 x 10~24t 1 -7 x 1CT24
[ast] The intensity is given for 158-5 Mc./s. and is twice that observed in one plane of polarization.
This intensity is taken from the spectrum of the radio source given by Stanley and Slee (ref. 2).
No visible remnant of the supernova of 1572 has yet been observed, and the integrated photographic magnitude given in Table 2 represents the upper limit to the intensity, as estimated by Baade11.
There is a difference of about 2-5 magnitudes between the intensities of the two radio sources, and this is equal to the difference between the apparent visual magnitudes reached by the supernovae at maximum brightness. There is, however, a much greater difference of at least 6 magnitudes between the integrated photographic magnitudes of the remnants of the supernovae. In view of the present lack of knowledge of the processes involved both in a supernova and in the emission of radio-frequency radiation from a localized source, it is not possible to offer any explanation of this discrepancy.
The discovery of a source in the position of the supernova (1572) supports the conclusion, originally based only on the observation of a source in the position of the Crab nebula7, that the remnant of a supernova is a source of intense radio-frequency radiation. This phenomenon is of great interest since no satisfactory mechanism for the generation of the radiation has yet been proposed. Further evidence could be gained by a careful search for a radio source in the position of the supernova of 1604, which unfortunately lies outside the field of the 218-ft. paraboloid. The region has already been surveyed by Stanley and Slee2 at 100 Mc./s.,.and no source in this position has been reported. However, their survey had a limit of detection of about 10~24 W./sq. m./cps., and the present results indicate that a source in the position of the supernova (1604) may have been overlooked.
The work has been carried out at the Jodrell Bank Experimental Station of the University of Manchester. We wish to thank Prof. Z. Kopal for directing our attention to the problem and Prof. A. C. B. Lovell for his interest in the investigation. One of us (R. H. B.) is indebted to Imperial Chemical Industries, Ltd., for a research fellowship, and the other (C. H.) to the Department of Scientific and Industrial Research for a maintenance grant.Bolton, , J. G., and Stanley, , G. J., Nature, 161, 312 (1948).ISIStanley, , G. J., and Slee, , O. B., Aust. J. Sci. Res., A, 3, 234 (1950).ISIRyle, , M., Smith, , F. G., and Elsmore, , B., Mon. Not. Roy. Ast. Soc., 110, 508 (1950).ISIHanbury Brown, , R., and Hazard, , C., Nature, 166, 901 (1950).ArticleHanbury Brown, , R., and Hazard, , C., Phil Mag., 43, 137 (1952).ISIWesterhout, , G., and Oort, , J. H., B.A.N., 11, 323 (1951).Bolton, , J. G., and Stanley, , G. J., Aust. J. Sci. Res., A, 2, 139 (1949).ISIHanbury Brown, , R., and Hazard, , C., Mon. Not. Roy. Ast. Soc. (in the press).Baade, , W. (private communication).Baade, , W., Astrophys. J., 96, 188 (1942).ArticleChemPortBaade, , W., Astrophys. J., 102, 309 (1945).ArticleISI