Apparent Angular Sizes of Discrete Radio Sources

The existence of discrete sources of extraterrestrial radio-frequency radiation is now well established1,2 and the positions of more than one hundred sources have been published3–5. Attempts to identify these sources with any particular class of visual object have so far failed, and the origin of the radiation remains unexplained. One of the fundamental requirements in the study of these sources is a knowledge of their apparent angular size, and although attempts to make this measurement have been made by several observers1–3, it has proved to be beyond the resolving power of their equipment. The present communication gives a preliminary account of a successful attempt to measure the angular size of the two most intense sources the positions6 and intensities4 of which are given in Table 1.