Page:Popular Science Monthly Volume 32.djvu/70

From Wikisource
Jump to: navigation, search
This page has been validated.
60
THE POPULAR SCIENCE MONTHLY.

from maximum to maximum being about eleven months. During about five months of that time it is completely invisible to the naked eye; then it begins to appear again, slowly increasing in brightness for some three months, until it shines as a star of the second magnitude, being then as bright as if not brighter than the most brilliant stars in the constellation. It retains this brilliancy for about two weeks, and

PSM V32 D070 Triangles andromeda and pegasus.jpg

Map 3.

then begins to fade again, and, in about three months, once more disappears. There are various irregularities in its changes, which render its exact period somewhat uncertain, and it does not always attain the same degree of brightness at its maximum. For instance, in 1779, Mira was almost equal in brilliancy to a first-magnitude star, but frequently at its greatest brightness it is hardly equal to an ordinary star of the second magnitude. Mira will attain its greatest brilliancy about the 2d of November, this year. By the aid of our little map you will readily be able to find it. You will perceive that it has a