Temporary stars are the rarest and most erratic of astronomical phenomena. The earliest records relating to them are not very clear, and we cannot in every instance be certain that it was one of these appearances that the ignorant and superstitious old chroniclers are trying to describe. The first temporary star that we are absolutely sure of appeared in 1572, and is known as “Tycho’s Star,” because the celebrated Danish astronomer (whose remains, with his gold-and-silver artificial nose—made necessary by a duel—still intact, were disinterred and reburied in 1901) was the first to perceive it in the sky, and the most assiduous and successful in his studies of it. As the first fully accredited representative of its class, this new star made its entry upon the scene with becoming _éclat._ It is characteristic of these phenomena that they burst into view with amazing suddenness, and, of course, entirely unexpectedly. Tycho’s star appeared in the constellation Cassiopeia, near a now well-known and much-watched little star named Kappa, on the evening of November 11, 1572. The story has often been repeated, but it never loses interest, how Tycho, going home that evening, saw people in the street pointing and staring at the sky directly over their heads, and following the direction of their hands and eyes he was astonished to see, near the zenith, an unknown star of surpassing brilliance. It outshone the planet Jupiter, and was therefore far brighter than the first magnitude. There was not another star in the heavens that could be compared with it in splendor. Tycho was not in all respects free from the superstitions of his time—and who is?—but he had the true scientific instinct, and immediately he began to study the stranger, and to record with the greatest care every change in its aspect. First he determined as well as he could with the imperfect instruments of his day, many of which he himself had invented, the precise location of the phenomena in the sky. Then he followed the changes that it underwent. At first it brightened until its light equaled or exceeded that of the planet Venus at her brightest, a statement which will be appreciated at its full value by anyone who has ever watched Venus when she plays her dazzling rôle of “Evening Star,” flaring like an arc light in the sunset sky. It even became so brilliant as to be visible in full daylight, since, its position being circumpolar, it never set in the latitude of Northern Europe. Finally it began to fade, turning red as it did so, and in March, 1574, it disappeared from Tycho’s searching gaze, and has never been seen again from that day to this. None of the astronomers of the time could make anything of it. They had not yet as many bases of speculation as we possess today. [Illustration: Chart showing location of Tycho’s star, 1572, and Nova Persei of 1901]