Lost and New Stars.
We may have perhaps read the “Lost Pleiad,” and wondered what has become of the star supposed to have dropped out of the cluster so well known in the constellation Taurus—the Pleiades. There are seven stars, of which six are visible to the average eye, and the ancients used to declare that one of the seven sisters (the daughters of Atlas and Pleione) hid herself because she had married a mortal, while all her sisters wedded gods. It is not improbable that one of the seven, formerly distinguishable with the unassisted eye, may have disappeared or been lost; but it is certain that strong eyesight can see more than seven now, and in the telescope there are about one hundred.
And it is a fact that some stars whose places have been carefully marked in the catalogue have subsequently disappeared. Many errors may have been made, and stars put down where no star existed, so a succeeding observer has not been able to find the star indicated. But, on the other hand, we may admit that stars have been lost to sight, and to compensate us for any such disappearances new stars are frequently observed, and these are very remarkable phenomena. About 121 B.C. Hipparchus perceived a new star, which was visible even in the daytime, and on subsequent occasions others came into existence—viz., in the years 945, 1264, and 1572. In the last-mentioned year Tycho Brahé suddenly perceived the new star, which was at first very brilliant. It grew fainter and fainter, after first gaining in intensity, and disappeared entirely in 1574; and at other times stars have been seen which remained only for a short time, and then disappeared.
The star discovered by Tycho Brahé was seen by him when walking across the fields one night, and he encountered peasants who were gazing at the new luminary. It was so bright that it threw a shadow from Brahé’s stick. The new arrival appeared in “Cassiopeia,” under the lady’s chair, forming, as pictured in the diagram, an irregular square. The strange star is the largest.
Fig. 622.—Cassiopeia.
Some stars exhibit extraordinary fluctuations, and one discovered by Mr. Birmingham in 1866, decreased rapidly and sank away to about the tenth magnitude, and then got brighter, and again diminished in splendour. The “Eta” Argûs has also been subjected to many fluctuations likewise, and such alterations have gained for these luminaries the name of “Variable Stars.”
Fig. 623.—Star-Map.
In the accompanying little chart there will be perceived two particular stars, named Algol, “the demon,” and Mira “the wonderful.” The latter is the most celebrated for its variable qualities, and its cycle of change occupies nearly one of our years. For a few days it appears very bright, and then fades away for about three months, to disappear for five months, and then it reappears again, increasing in brilliancy up to the second magnitude for another three months or so. Some people account for these phenomena by stating that the sides of the star being less luminous present the dark and light portions in rotation; but we can give no satisfactory explanation of the reason, unless it be caused by an aggregation of spots upon its surface, like sun-spots on our sun, or perhaps by eclipse.