Fig. 23.—Position of Leo, Source of the Leonids
Among the constellations there is a fine sickle-shaped group, forming a part of Leo, one of the signs of the Zodiac. That part of the sky defined by Leo is curiously related to the meteors of the 12th to the 14th of November. Every shooting star truly belonging to that great shower pursued a track across the heavens, the direction of which, if carried back far enough, was always found to pierce through the sickle of Leo. Indeed, the paths of all the meteors formed a set of rays spreading away from that one point in the constellation. An invariable characteristic of this particular shower is its connection with the constellation of Leo, hence the appropriateness of the name of Leonids.
It must be borne in mind that we can never see the meteors until the fatal moment when they dive into our atmosphere. We could, indeed, at any time point our telescope to the spot in the heavens where we know the great shoal must certainly be located. But the mightiest telescope in the world does not disclose the shoal to us. In fact, we would never have seen these Leonids at all, we would never have become conscious that such a shoal of meteors existed, had it not been for a certain circumstance, which, for want of a better expression, I must speak of as accidental.
Our globe pursues a certain definite track around the sun. Year after year, with undeviating regularity, the earth performs the stages of its journey. If it reaches certain points on the 1st of January and the 12th of October in one year, then it reaches the same points on the 1st of January and the 12th of October respectively on next year, or any other year.
The Leonids and the earth have each a certain track. It might of course have happened that one of these tracks lay quite outside or quite inside the other. In the case of the Leonids, it has chanced that their orbit does intersect the orbit of the earth, and to this circumstance we are indebted for the glorious displays every thirty-three years.
There are many other periodic showers of shooting stars besides those notable Leonids. None of the other showers, however, possess the same importance as the Leonids, nor do they ever manifest celestial splendor comparable with that of those of the 13th of November. The Perseids, for example, which appear from the 9th to the 11th of August, are tolerably constant in their appearance, but have little spectacular interest. There is also another shower called the Andromedes, which occurs on the 27th of November. It has produced certain displays, one of the most remarkable of which took place in 1872. The meteors were excessively numerous on that occasion, but they were so short in their paths, and so insignificant as to brilliance, that the spectacle, though of great scientific interest, could not be compared as to splendor with that of the Leonids in 1866.
There are also several other showers which appear with greater or less regularity. Each of these possesses two distinct characteristics by which its meteors can be identified. One of these characters is the date on which the shower appears. The other is the constellation or point on the heavens from which all the meteors appear to radiate. Thus when we speak of the Andromedes on the 27th of November, we express that the shower on the 27th November comes from the part of the heavens marked by the constellation of Andromeda.
A striking discovery has been made which points to a curious connection between comets and shooting stars. It has been found that the track followed by a great shower of meteors is often identical with the track pursued by a comet. It is wholly beyond the province of mere chance that an orbit such as that of the Leonids should, both as to its size and its position in space, be likewise that of a comet, unless the comet and the meteor swarm were objects related to each other.
The great sun guides our world through its long annual journey. The mighty mass of the earth yields compliance to the potent sway of the ruler of our system. But the sun does not merely exercise a control over the vast planets which circulate around him. The supreme law of gravitation constrains the veriest mote that ever floated in a sunbeam, with the same unremitting care that it does the mightiest of planets. Thus it is that each little meteor is guided in its journeys for untold ages. Each of these little objects hurries along, deflected at every moment, to follow its beautifully curved path by the incessant attraction of the sun. At last, however, the fatal plunge is taken. The long wanderings of the meteor have come to an end and it vanishes in a streak of splendor.