VIII.—The Oxford New Star.
A PAIR OF PHOTOGRAPHS TAKEN AT THE HARVARD COLLEGE OBSERVATORY BEFORE AND AFTER ITS APPEARANCE
(The arrow indicates the place of the new star. It will be seen that the left-hand picture though it shews fainter stars than the other, has not a trace of the new star.)

Dr. Anderson.

Generally these stars have been noted by eye observation, as in the case of the two found by Dr. Anderson of Edinburgh. In these cases also we may say that deliberate search was rewarded; for Dr. Anderson is probably the most assiduous “watcher of the skies” living, though he seldom uses a telescope; sometimes he uses an opera-glass, but usually the naked eye. He describes himself as an “Astrophil” rather than as an astronomer. “I love the stars,” he says; “and whenever they are shining, I must be looking.” And so on every fine night he stands or sits at his open study window gazing at the heavens. I believe he was just about to leave them for his bed, near 3 A.M. on the night of February 21, 1901, when, throwing a last glance upward, he suddenly saw a brilliant star in the constellation Perseus.Nova Persei. His first feeling was actually one of disappointment, for he felt sure that this object must have been there for some time past without his knowing of it, and he grudged the time lost when he might have been regarding it. More in a spirit of complaint than of inquiry, he made his way to the Royal Observatory at Edinburgh next day to hear what they had to say about it, though he found it difficult to approach the subject. He first talked about the weather, and the crops, and similar topics of general interest; and only after some time dared he venture a casual reference to the “new portent in the heavens.” Seeing his interlocutor look somewhat blank, he ventured a little farther, and made a direct reference to the new star in Perseus; and then found to his astonishment, as also to his great delight, that he was the first to bring news of it. The news was soon communicated to other observers; all the telescopes of the world were soon trained upon it; and this wonderful “new star of the new century” has taught us more of the nature of these extraordinary bodies than all we knew before.

Records previous to discovery.

Perhaps I may add a few remarks on one or two features of these bodies. Firstly, let us note that Professor Pickering of Harvard is now able to make a most important contribution to the former history of these objects—that is to say, their history preceding their actual detection. We remember that, after Uranus had been discovered, it was found that several observers had long before recorded its place unknowingly; and similarly Professor Pickering and his staff have usually photographed other new objects unknowingly. There are on the shelves at Harvard vast stores of photographs, so many that they are unable to examine them when they have been taken; but once any object of interest has been discovered, it is easy to turn over the store and examine the particular plates which may possibly show it at an earlier date. In this way it was found that Dr. Anderson’s new star had been visible only for a few days before its discovery, there being no trace of it on earlier plates. Similarly, in the case of the new star found at Oxford, plates taken on March 1st and 6th, fifteen days and ten days respectively before the discovery-plate of March 16th, showed the star. But, in this particular instance, greater interest attaches to two still earlier plates taken elsewhere, and with exposures much longer than any available at Harvard. One had been obtained at Heidelberg by Dr. Max Wolf, and another at the Yerkes Observatory of Chicago University, by Mr. Parkhurst; and on both there appeared to be a faint star of about the fourteenth or fifteenth magnitude, in the place subsequently occupied by the Nova; and the question naturally arose,Was Nova Geminorum previously shining faintly? Was this the object which ultimately blazed up and became the new star? To settle this point, it was necessary to measure its position, with reference to neighbouring stars, with extreme precision; and here it was unfortunate that the photographs did not help us as much as they might, for they were scarcely capable of being measured with the requisite precision. The point was an important one, because if the identity of the Nova with this faint star could be established, it would be the second instance of the kind; but so far as they went, measurements of the photographs were distinctly against the identity. Such was the conclusion of Mr. Parkhurst from his photograph alone; and it was confirmed by measures made at Oxford on copies of both plates, which were kindly sent there for the purpose. The conclusion seemed to be that there was a faint star very near, but not at, the place of the new star; and it was therefore probable that, although this faint star was temporarily invisible from the brightness of the adjacent Nova, as the latter became fainter (in the way with which we have become familiar in the case of new stars), it might be possible to see the two stars alongside each other. The suspicion negatived.This critical observation was ultimately made by the sharp eyes of Professor Barnard, aided by the giant telescope of the Yerkes Observatory; and it seems clear therefore that the object which blazed up to become the Nova of 1903 could not have previously been so bright as a faint star of the fourteenth magnitude. Although this is merely a negative conclusion, it is an important one in the history of these bodies.

The second point to which I will draw your attention is from the history of the other Nova just mentioned—Dr. Anderson’s New Star of 1901. In this instance it is not the history previous to discovery, but what followed many months after discovery, that was of engrossing interest; and again Yerkes Observatory, with its magnificent equipment, played an important part in the drama.Nebula round Nova Persei.
Its changes. When, with its giant reflecting telescope, photographs were taken of the region of Nova Persei after it had become comparatively faint, it was found that there was an extraordinarily faint nebulosity surrounding the star. Repeating the photographs at intervals, it was found that this nebulosity was rapidly changing in shape. “Rapidly” is, of course, a relative term, and a casual inspection of two of the photographs might not convey any impression of rapidity; it is only when we come to consider the enormous distance at which the movements, or apparent movements, of the nebulæ must be taking place that it becomes clear how rapid the changes must be. It was not possible to determine this distance with any exactness, but limits to it could be set, and it seemed probable that the velocity of the movement was comparable with that of light.Due to travelling illumination. The conclusion suggested itself that the velocity might actually be identical with that of light, in which case what we saw was not the movement of actual matter, but merely that of illumination, travelling from point to point of matter already existing.

SEPT. 20, 1901

NOV. 13, 1901