The Discovery of Our Galaxy by Charles A. Whitney

Author:Charles A. Whitney [Whitney, Charles A.]
Language: eng
Format: epub
ISBN: 978-0-307-81709-9
Publisher: Knopf Doubleday Publishing Group
Published: 2012-04-25T04:00:00+00:00

Concerning variations of stellar brightness and color, astronomers no longer agree with Laplace that spots on the surface of a star will account for most of the observations. Many stars undergo periodic swelling and shrinking; this fact is directly proven by variations of the velocity of the atmospheric gases. Pairs of stars also show periodic variations if the orbits are arranged so that they alternately block each other’s light.

… Other stars have appeared quite suddenly and then have disappeared after several months. (One example of this was the star observed by Tycho Brahe in 1572, in the constellation Cassiopeia. It quickly surpassed the brightest stars, even Jupiter, and it was seen in the daytime. Its light then decreased and it vanished sixteen months after its discovery. Its color varied widely: it was first dazzling white, then reddish yellow and finally a leaden white like Saturn.) What amazing changes must have occurred on these great bodies to be observed from our distance. Think, how they must surpass what we see on the surface of the sun, and what convincing proof they give that nature is not everywhere and always the same. All such stars which again became invisible remained in precisely the same position during their apparition; thus, there exist large bodies in space, perhaps as numerous as the stars.

A luminous star of the density of the earth, and having a diameter two hundred and fifty times that of the sun would not, by virtue of its gravitational attraction, let any of its light escape to us. Thus, it is possible that the largest luminous bodies of the universe are, for that very reason, invisible.

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