CHAPTER I

THE HEAVENS WE SEE

THE earth is a speck in the infinite ocean of space. Surrounding it at immense distances on all sides are the stars, each a sun comparable to our own in magnitude, but sunk so deep in the depths of space that it appears as a lucid point. Though it may seem a hopeless task to attempt to count the stars, in reality the number visible to the naked eye is comparatively small. On a very fine night it is possible to reckon between two and three thousand stars at one time, but such favourable opportunities are not of common Occurrence. A little mist or fog is usually present which blots out all the fainter stars, reducing the number of those the light of which can pierce the veil to about one thousand. And though the glare of moonlight adds to the beauty of a night-scene, it assimilates the feeble beams of many of the distant suns and causes all to undergo an apparent diminution of brilliancy. By the invention of the telescope, however, the observable stellar universe became enormously increased, hence when Galileo turned his optic-tube towards the heavens he discovered "world beyond world, in infinite

extent, profusely scatter'd o'er the blue immense." Telescopes have increased in size since that day, and with the mighty instruments now at the disposal of astronomers something like one hundred millions of stars are brought within view.

One of the first circumstances that strikes the observer who directs his inquiring gaze heavenwards, is that the brighter stars form well-marked groups which constantly retain the same shape. A very conspicuous configuration or constellation of this kind can be seen when looking towards the north on any fine night. It is made up of seven stars, and, in general language, is known as the Plough or Charles' Wain. Astronomers name the group Ursa Major, that is, the Great Bear. To the ancients, this and other conspicuous groups of stars bore a fancied resemblance to figures of men and animals, or some peculiarity was attributed to them which was also possessed by characters in heathen mythology. The Egyptians, Chaldeans, and Chinese were the first peoples who divided up the stars in this manner, but the earliest systematic grouping is contained in the Almagest, a great work written by Ptolemy nearly eighteen hundred years ago. In that catalogue the stars are divided into forty-eight groups, most of them being named after characters connected with the voyage of the ship Argo. It requires a vivid imagination to construct these figures from the configuration of the stars. It is doubtful, indeed, whether any of the constellations were ever supposed really to resemble the characters whose names they bear. There would be mythological reasons why certain figures should appear near to each other in the sky, and it would be a matter of chance whether

the stars lent themselves to the required configuration or not, the artist using the existing material in any manner he pleased. The figures were probably sketched upon a globe to represent constellations, and only those stars which fell within the outlines of the drawings were assumed to belong to the constellation. This is strongly supported by the fact that many bright stars were not included in any constellation; thus a bright star named Arcturus is not contained in Ptolemy's constellation Bootes, to which it properly belongs.

In spite of the unscientific plan adopted by ancient astronomers in mapping the heavens, the arbitrary division is still retained for convenience. The constellations may thus be considered analogous to countries on the earth, with the stars as towns. The majority of the bright stars possess proper names, such, for example, as Regulus, Aldebaran, and Rigel, but another and a better method of designating them is by means of the letters of the Greek alphabet, giving the first letter (Alpha) to the brightest star in a constellation, the second to the next brightest, and so on. Thus, Regulus is a Leonis, that is, Alpha of the Lion constellation; Aldebaran is a Tauri, that is, Alpha of the Bull, and Rigel is B Orionis-Beta of Orion.

It is now possible to follow with interest a description of the arrangement of the stars in some of the chief constellations. But this portion of astronomy can only be properly understood by looking at the evening sky. All that can be done here is to point out conspicuous configurations of stars to act as celestial finger-posts.

The Great Bear constellation is always visible in England on a fine night, and is therefore a useful

starting-point. The seven stars which compose it are easily recognised when looking towards the north, and the two most distant from the curved tail serve to indicate the position of a star which should be familiar to

FIG. 1.-View of the sky looking north. To find the aspect of the circumpolar constellations at about 10 P.M. during any season of the year, turn the page until the name of the season is at the bottom.

every one. The objects in question are known as the "Pointers," because the line joining them points very nearly to the Pole-Star or North Star (Fig. 1). This star never sinks below the horizon of an observer in England, and when facing it we face the north. It appears to

occupy the same position in the sky night after night throughout the year, differing in this respect from all others-a peculiarity referred to by Shakespeare in the following lines:

Constant as the northern star,
Of whose true-fix'd and resting quality
There is no fellow in the firmament.

The skies are painted with unnumber'd sparks,
They are all fire and every one doth shine,
But there's but one in all doth hold his place.

Near the Pole-Star can be seen two other fairly bright stars, known as the "Guards of the Pole."

After the Great Bear, the next most conspicuous group in the northern sky belongs to the constellation of Cassiopeia. Its characteristic form is that of a W-a -a configuration termed Cassiopeia's Chair. A line from the last star in the tail of the Great Bearη Ursae Majoris-if carried through the Pole-Star and continued for about the same distance on the other side, leads to this group, the top of the W being directed towards the Pole. Whatever the position in which the Great Bear is seen, Cassiopeia appears on the opposite side of the Pole.

Between the Great Bear and the "Guards," and extending round to Cassiopeia, occur the constellations Draco and Cepheus. Neither of these groups are marked by any very definite figures, but it is not difficult to find the stars in them by reference to a map of the northern region of the sky.

The Great and Little Bears, and Cassiopeia, are always visible on a fine night in England. Sometimes they are high above the northern horizon, sometimes low down, but never invisible unless shut