ASTRONOMY. INTRODUCTORY CHAPTER. 1. ASTRONOMY is that branch of NATURAL SCIENCE which treats of the MAGNITUDES, DISTANCES, CONSTITUTIONS, and MOTIONS of the HEAVENLY BODIES, and the LAWS which regulate them. 2 2. THE HEAVENLY BODIES consist of moons, planets,1 comets, and suns; and possibly a fifth class exist called nebula. To moons, planets, and suns the general name of stars is often given. 3. No heavenly body is independent of another. Each exists and moves as a part of one vast and harmonious combination, termed the UNIVERSE. The Visible Heavens are a portion of this Universe. How great or how small a portion we cannot say; for the rest, shrouded from our view in the depths of space, lies beyond the limits of our knowledge. 4. The mode of union existing among the heavenly bodies is the following: One or more moons revolve 1. Planet, from the Greek word planëtes, signifying a wanderer, a star that changes its place in the heavens. 2. Comet, from the Latin word coma, a head of hair, this body present ing a hairy appearance. 3. The name of nebula is given by astronomers to certain objects in the distant heavens which appear like small clouds, or specks of mist. True nebulæ are supposed to be vast collections of unformed matter, thinly diffused through space. Nebula is a Latin word, signifying mists, or clouds. What is Astronomy? What do the heavenly bodies consist of? Does a heavenly body exist and move independent of others? What is said of the visible heavens? What is the mode of union between heavenly bodies? about a planet; several planets with their attendant moons revolve about a sun, around which, likewise, sweeps a numerous train of comets. A sun with its assemblage of planets and comets constitutes a system. 5. The investigations of astronomers tend to prove that these systems are not fixed in space, but revolve like planets about some common central point, or body. And we have reason for believing that this mode of arrangement extends throughout all space, groups of systems rising one above the other in magnitude; the lesser circling around the greater, until at length their vast aggregate embraces and completes the Universe. 6. SOLAR SYSTEM. The sun with his train of planets, moons, and comets, forms the SOLAR SYSTEM. The number of planets already known is forty-one. Thirty of these have been discovered within the last ten years, and others will doubtless be detected. The names of the planets, with the symbols assigned them, are given in the following table, in the order of their distances from the sun, beginning with the nearest. What is a system? Explain the term universe. What is the solar system? How many planets are now known? How many have been discovered within the last ten years? Give the names of the planets? |
