12 Canum Venaticorum, 2½ and 6½. White and red, Sir William Herschel; but Sir John Herschel says in 1830, “With all attention I could perceive no contrast of colours in the two stars.” Struve found them both white in 1830, thus agreeing with Sir John Herschel. Sestini saw them yellow and blue in 1844; Smyth, in 1855, pale reddish white and lilac; Dembowski, in 1856, white and pale olive blue; and Webb, in 1862, flushed white and pale lilac.
On October 13, 1907, Nova Persei, the great new star of 1901, was estimated to be only 11·44 magnitude, or about 11½. When at its brightest this famous star was about zero magnitude; so that it has in about 6 years faded about 11½ magnitudes in brightness; in other words, it has been reduced to 1⁄40000 of its greatest brilliancy!
CHAPTER XVII
Nebulæ and Clusters
In his interesting and valuable work on “The Stars,” the late Prof. Newcomb said—
“Great numbers of the nebulæ are therefore thousands of times the dimensions of the earth’s orbit, and most of them are thousands of times the dimensions of the whole solar system. That they should be completely transparent through such enormous dimensions shows their extreme tenuity. Were our solar system placed in the midst of one of them it is probable that we should not be able to find any evidence of its existence”!
Prof. Perrine thinks that the total number of the nebulæ will ultimately be found to exceed a million.[352]
Dr. Max Wolf has discovered a number of small nebulæ in the regions near Algol and Nova Persei (the great “new star” of 1901). He says, “They mostly lie in two bands,” and are especially numerous where the two bands meet, a region of 12 minutes of arc square containing no less than 148 of them. They are usually “round with central condensation,” and form of Andromeda nebula.[353]