Cosmic Radiations at 5 Metres Wave-length

Abstract

THE discovery of electromagnetic 'noise' radiations at radio frequencies was first made by K. G. Jansky¹ who, in a series of measurements at about 20 Mc. s. ( 15 m.) was able to establish the close connexion between the direction of greatest intensity and the centre of the galaxy. G. Reber² later made measurements at 160 Mc./s. ( 2 m.), and he was able, by virtue of a narrower beam, to detect a number of subsidiary peaks. He found the intensity of radiation at this higher frequency was very much less ; he also suggested a probable explanation of the radiations, namely, the interactions in encounters between positive ions and free electrons released from interstellar gases by the photoelectric action of stellar radiations. The theoretical treatment for radiation arising from such encounters was first given by H. A. Kramers³ to account for continuous radiation in X-ray spectra. The cosmic noise radiation is not observable at frequencies lower than a few megacycles per second, owing to the screening action of the ionosphere.