The normal radio wave emission from the sun amounts to 10-17 of the heat radiation, and increases during bursts1 to as much as 10-13. If a radio star, e.g., the source in Cygnus, is situated at a distance of 100 light years, its radio emission is of the order of 10-4 of the heat radiation of our sun. It is very un-likely that the atmosphere of any star could be so different from the sun’s atmosphere as to allow a radio emission which is 109 to 1013 times greater, and it seems therefore to be excluded that the source could be as small as a star. The recent discovery2 that the intensity variations of radio stars is a “twinkling” makes it possible to assume larger dimensions.