XI OCTOBER
The constellations that will be found nearest the meridian in early October evenings are the circumpolar constellations Cepheus and Cassiopeia, and in the southern sky, Capricornus and Aquarius.
Cepheus, The King, and Cassiopeia, his Queen, of whom we shall have more to say later in connection with the constellations of Andromeda and Perseus, sit facing the north pole of the heavens opposite Ursa Major, The Great Bear, familiar to us under the name of The Big Dipper. The foot of Cepheus rests upon the tail of the Little Bear, and the star farthest north in the diagram is in the left knee. The head is marked by a small triangle of faint stars, shown in the diagram. One of these three faint stars—the one farthest east—known as Delta Cephei, is a very remarkable variable star, changing periodically in brightness every five and one-third days. Its name has been given to a large class of variable stars—the Cepheid variables—that resemble Delta Cephei in being giant suns, faint only because they are at very great distances from the earth, and varying in brightness with the greatest regularity in periods that range from a few hours to several weeks. It has been found that the longer the period of light change the greater is the star in size and brightness. The Cepheids of longest period are 10,000 times more brilliant than our own sun. Cepheus contains no very bright or conspicuous stars. Alpha Cephei, the brightest star in the group, marks The King's right shoulder. It is the star farthest to the west in the diagram, and is only a third-magnitude star.
October—Cassiopeia and Cepheus
Cassiopeia is a constellation with which every one in the northern hemisphere should be familiar, owing to its very distinctive W-shape and its far northern position, which brings it conspicuously into view throughout the clear fall and winter evenings. Cassiopeia is pictured in all star atlases that show the mythological figures, with her face toward the north pole. The stars in the W outline the body. Alpha, the star farthest south in the diagram marks the breast of Cassiopeia. Her head and uplifted hands are represented by faint stars south of Alpha. This star is occasionally referred to by its Arabic name of Schedir. Beta, the leader of all the stars in the W in their daily westward motion, is also known by an Arabic name, Caph.
In the constellation of Cassiopeia there appeared in the year 1572 A.D., a wonderful temporary star which suddenly, within a few days' time, became as brilliant as the planet Venus and was clearly visible in broad daylight. This star is often referred to as Tycho's Star, because it was observed, and its position very accurately determined, by Tycho Brahe, one of the most famous of the old astronomers. This star remained visible to every one for about sixteen months, but it finally faded completely from view, and it is believed that a faint, nebulous red star, visible only in the telescope and close to the position recorded by Tycho, represents the smoldering embers of the star that once struck terror to the hearts of the superstitious and ignorant among all the nations of Europe, who took it to be a sign that the end of the world was at hand.
Both Cassiopeia and Cepheus lie in the path of the Milky Way, which reaches its farthest northern point in Cassiopeia and passes from Cepheus in a southerly direction into the constellation of Cygnus.
October—Aquarius and Capricornus
Turning now to southern skies, we find on and to the west of the meridian at this time the rather inconspicuous zodiacal constellation of Capricornus, The Goat. It contains no stars of great brightness and is chiefly remarkable for the fact that it contains one of the few double stars that can be seen without the aid of a telescope. The least distance in the heavens that the unaided human eye can separate is about four minutes of arc. The star Alpha in Capricornus is made up of two stars separated by a distance of six minutes of arc, so that any one can readily see that it consists of two stars very close together. This star, Alpha, will be found in the extreme western part of the constellation, and can best be located in conjunction with the star Beta, which is slightly brighter and lies but a short distance almost due south of Alpha, the two stars standing somewhat alone in this part of the heavens.
To the north and east of Capricornus we find Aquarius, which is also a zodiacal constellation. Aquarius is the Water-Bearer, and the water jar which he carries is represented by a small, but distinct, Y of stars from which flows a stream of faint stars toward the southeast and south. Aquarius, like Capricornus, is a rather uninteresting constellation, as it is made up of inconspicuous third- and fourth-magnitude stars. The entire region covered by these two groups of stars is remarkably barren, since it contains not a single first- or even second-magnitude star and little to attract the observer's eye.
To relieve the barrenness of this region, there appears just to the south of Aquarius and southeast of Capricornus, sparkling low in the southern sky on crisp October evenings, the beautiful first-magnitude star Fomalhaut in the small southern constellation of Piscis Australis, The Southern Fish. This star is the farthest south of all the brilliant first-magnitude stars that can be seen from the middle latitudes of the Northern Hemisphere. The constellation in which it lies is so close to the southern horizon in our latitudes that it cannot be seen to any advantage, and it is at best very inconspicuous, containing no other objects of interest. Fomalhaut cannot be mistaken for any other star visible at this time of year in the evening, since it stands in such a solitary position far to the south. At the time of which we are writing it will be found a few degrees east of the meridian.