By 14 January he had nearly finished the whole pile. In the evening he decided to go back to the Observatory. The afternoon he had spent at the California Institute of Technology, where there had been an interesting seminar on the subject of the spiral arms of the galaxies. There had been quite a discussion after the seminar. Indeed he and his friends had argued throughout dinner about it and during the drive back to the Observatory. He reckoned he would just about get through the last batch of plates, the ones he had taken on the night of 7 January.
He finished the first of the batch. It turned out a finicking job. Once again, every one of the ‘possibilities’ resolved into an ordinary, known oscillator. He would be glad when the job was done. Better to be on the mountain at the end of a telescope than straining his eyes with this damned instrument, he thought, as he bent down to the eye-piece. He pressed the switch and the second pair flashed up in the field of view. An instant later Jensen was fumbling at the plates, pulling them out of their holders. He took them over to the light, examined them for a long time, then replaced them in the ‘blinker’ and switched on again. In a rich star field was a large, almost exactly circular, dark patch. But it was the ring of stars surrounding the patch that he found so astonishing. There they were, oscillating, blinking, all of them. Why? He could think of no satisfactory answer to the question, for he had never seen or heard of anything like this before.