Even these changes, however, though justly regarded as among the chief wonders and mysteries of the star-depths, seem in turn to sink into nothingness by comparison with the sudden appearance of a new star, as interpreted by modern scientific observations. Of old, when a new star appeared, it was thought for awhile to be a fresh creation; a new sun set in the centre of a new system of worlds,--a thought which was not then so startling as in our own times it would be reckoned. When the new star was seen slowly to die out until at last it became invisible, men were content to regard it as a sign set in the heavens for a special purpose. Nor did they find much difficulty in associating such a phenomenon with some event of importance occurring during its continuance, or soon after the new star had died out. Such were the explanations offered respecting the exceedingly bright star which made its appearance in the constellation Cassiopeia in the year 1572. The place in which it appeared is shown in fig. 7. It must have sprung into its full glory in a very short time, for Tycho Brahé, the celebrated astronomer, tells us that, returning on November 1, 1572, from his laboratory to his dwelling-house, he saw the new star, which he was certain had not been visible an hour before, shining more brightly than any before seen. It surpassed all the stars in the heavens in brilliancy, and even Jupiter when that planet is at its brightest. Only Venus at her brightest was superior to the new star. For three weeks it shone with full lustre, after which it began slowly to decline. Being situated in a part of the heavens always above the horizon (for European observatories), the star's entire history could be followed. It remained for sixteen months steadfast in its position like the other stars. As it decreased in size it varied in colour. "At first," says an old writer; "its light was white and extremely bright; it then became yellowish; afterwards of a ruddy colour like Mars; and finished with a pale, livid white, resembling the colour of Saturn." [Illustration: Fig. 7.--Cassiopeia; showing where a new star appeared in the year 1572.]