Those who care to look occasionally at the heavens to know whether this star has returned to view may be interested to learn whereabouts it should be looked for. The place may be described as close to the back of the star-gemmed chair in which Cassiopeia is supposed to sit—a little to the left of the seat of the chair, supposing the chair to be looked at in its normal position. But as Cassiopeia's chair is always inverted when the constellation is most conveniently placed for observation, and indeed as nine-tenths of those who know the constellation suppose the chair's legs to be the back, and vice versâ, it may be useful to mention that the star was placed somewhat thus with respect to the straggling W formed by the five chief stars of Cassiopeia. There is a star not very far from the place here indicated, but rather nearer to the middle angle of the W. This, however, is not a bright star; and cannot possibly be mistaken for the expected visitant. (The place of Tycho's star is indicated in my School Star-Atlas and also in my larger Library Atlas. The same remark applies to both the new stars in the Serpent-Bearer, presently to be described.)
In August 1596 the astronomer Fabricius observed a new star in the neck of the Whale, which also after a time disappeared. It was not noticed again till the year 1637, when an observer rejoicing in the name of Phocyllides Holwarda observed it, and, keeping a watch, after it had vanished, upon the place where it had appeared, saw it again come into view nine months after its disappearance. Since then it has been known as a variable star with a period of about 331 days 8 hours. When brightest this star is of the second magnitude. It indicates a somewhat singular remissness on the part of the astronomers of former days, that a star shining so conspicuously for a fortnight, once in each period of 331-1⁄3 days, should for so many years have remained undetected. It may, perhaps, be thought that, noting this, I should withdraw the objection raised above against Sir J. Herschel's idea that the star in Cassiopeia may return to view once in 156 years, instead of once in 312 years. But there is a great difference between a star which at its brightest shines only as a second-magnitude star, so that it has twenty or thirty companions of equal or greater lustre above the horizon along with it, and a star which surpasses three-fold the splendid Sirius. We have seen that even in Tycho Brahe's day, when probably the stars were not nearly so well known by the community at large, the new star in Cassiopeia had not shone an hour before the country people were gazing at it with wonder. Besides, Cassiopeia and the Whale are constellations very different in position. The familiar stars of Cassiopeia are visible on every clear night, for they never set. The stars of the Whale, at least of the part to which the wonderful variable star belongs, are below the horizon during rather more than half the twenty-four hours; and a new star there would only be noticed, probably (unless of exceeding splendour), if it chanced to appear during that part of the year when the Whale is high above the horizon between eventide and midnight, or in the autumn and early winter.
It is a noteworthy circumstance about the variable star in the Whale, deservedly called Mira, or The Wonderful, that it does not always return to the same degree of brightness. Sometimes it has been a very bright second-magnitude star when at its brightest, at others it has barely exceeded the third magnitude. Hevelius relates that during the four years between October 1672 and December 1676, Mira did not show herself at all! As this star fades out, it changes in colour from white to red.
Towards the end of September 1604, a new star made its appearance in the constellation Ophiuchus, or the Serpent-Bearer. Its place was near the heel of the right foot of 'Ophiuchus huge.' Kepler tells us that it had no hair or tail, and was certainly not a comet. Moreover, like the other fixed stars, it kept its place unchanged, showing unmistakably that it belonged to the star-depths, not to nearer regions. 'It was exactly like one of the stars, except that in the vividness of its lustre, and the quickness of its sparkling, it exceeded anything that he had ever seen before. It was every moment changing into some of the colours of the rainbow, as yellow, orange, purple, and red; though it was generally white when it was at some distance from the vapours of the horizon.' In fact, these changes of colour must not be regarded as indicating aught but the star's superior brightness. Every very bright star, when close to the horizon, shows these colours, and so much the more distinctly as the star is the brighter. Sirius, which surpasses the brightest stars of the northern hemisphere full four times in lustre, shows these changes of colour so conspicuously that they were regarded as specially characteristic of this star, insomuch that Homer speaks of Sirius (not by name, but as the 'star of autumn') shining most beautifully 'when laved of ocean's wave'—that is, when close to the horizon. And our own poet, Tennyson, following the older poet, sings how
the fiery Sirius alters hue,
And bickers into red and emerald.
The new star was brighter than Sirius, and was about five degrees lower down, when at its highest above the horizon, than Sirius when he culminates. Five degrees being equal to nearly ten times the apparent diameter of the moon, it will be seen how much more favourable the conditions were in the case of Kepler's star for those coloured scintillations which characterised that orb. Sirius never rises very high above the horizon. In fact, at his highest (near midnight in winter, and, of course, near midday in summer) he is about as high above the horizon as the sun at midday in the first week in February. Kepler's star's greatest height above the horizon was little more than three-fourths of this, or equal to about the sun's elevation at midday on January 13 or 14 in any year.
Like Tycho Brahe's star, Kepler's was brighter even than Jupiter, and only fell short of Venus in splendour. It preserved its lustre for about three weeks, after which time it gradually grew fainter and fainter until some time between October 1605 and February 1606, when it disappeared. The exact day is unknown, as during that interval the constellation of the Serpent-Bearer is above the horizon in the day-time only. But in February 1606, when it again became possible to look for the new star in the night-time, it had vanished. It probably continued to glow with sufficient lustre to have remained visible, but for the veil of light under which the sun concealed it, for about sixteen months altogether. In fact, it seems very closely to have resembled Tycho's star, not only in appearance and in the degree of its greatest brightness, but in the duration of its visibility.
In the year 1670 a new star appeared in the constellation Cygnus, attaining the third magnitude. It remained visible, but not with this lustre, for nearly two years. After it had faded almost out of view, it flickered up again for awhile, but soon after it died out, so as to be entirely invisible. Whether a powerful telescope would still have shown it is uncertain, but it seems extremely probable. It may be, indeed, that this new star in the Swan is the same which has made its appearance within the last few weeks; but on this point the evidence is uncertain.