In 1931 he began to study atmospheric ‘static’ that interfered with telecommunications. By the end of 1932 he had accounted for all but one persistent signal, which he concluded came from outside the Solar System in the direction of the constellation Sagittarius, towards the centre of our Galaxy. Thus was born radio astronomy, although Jansky himself never followed up his discovery. In radio astronomy, the unit of flux density is now named the jansky in his honour.