Page:The Music of the Spheres.djvu/75

 which had previously been blank, a new star shone forth. This star glowed as brightly as the planet Venus, which outshines every star in the sky. It was so bright that it was even visible in the daytime! This brilliancy then commenced to diminish, the star growing fainter and fainter until in about a year and a half it had completely disappeared.

While new stars have been noted during the course of centuries, the appearance of one is always so unusual that it stands out against the background of the sky with almost a disquieting effect. The presence of an additional bright star, strange as it may seem, is immediately noticeable to one who is familiar with the constellations. Astronomers record its history with as much interest as the appearance of a new island or volcano would occasion on earth.

Two theories for temporary stars are given in Moulton's "Introduction to Astronomy." Professor Moulton tells us that these theories are surrounded by serious objections—but they are interesting nevertheless.

One is "that there is invisible nebulous or meteoric matter lying in various parts of space, particularly in the region occupied by the Milky Way (there is confirmatory evidence of this hypothesis); that there are also dark or very faint stars"—(that is stars which are in the last stages of cooling, a phenomenon also confirmed)—"that the dark stars, rushing through the nebulæ, blaze into incandescence as meteors glow when they enter the earth's atmosphere; that the heating is superficial and quickly dies away." Another hypothesis is that temporary stars "are produced by collisions of stars with stars."

Still another hypothesis among astronomers which has lately gained considerable support is that at the time of an outbreak in a typical nova (new star), a shell of incandescent gas is actually ejected at an enormous rate of speed. Such a phenomenon has been witnessed in the case of one very recent nova.