An Introduction to Astronomy: Designed as a Textbook for the Use of Students of Yale CollegeCollins, Keese, & Company, 1839 - 276 pages |
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Common terms and phrases
altitude angular distance aphelion apparent diameter appear apsides astronomical axis azimuth celestial celestial sphere clock comet conjunction declination degree density described determined direction disk diurnal motion diurnal revolution earth earth's orbit ecliptic elevation equal equator equinoctial figure force gravity greater greatest heavenly bodies heavens Hence horizon horizontal parallax hour inclination inferior conjunction inferior planet Jupiter latitude learner light limb longitude lunar measured Mercury meridian meridian altitude miles moon moon's motion move nearly node oblique observations opposite parallel passes perigee perihelion period perpendicular planet planetary polar pole quadrant quantity of matter refraction represent revolves right angles right ascension ring satellites seen semi-diameter shadow side sidereal day solar day solstice spectator sphere star sun and moon sun's superior planets surface telescope tides tion triangle tropic Uranus velocity Venus vernal equinox vernier vertical circle west to east zenith distance
Popular passages
Page 89 - GRAVITATION, is that influence by which every body in the universe, whether great or small, tends towards every other, with a force which is directly as the quantity of matter, and inversely as the square of the distance.
Page 255 - Another, in the constellation Andromeda, presents a visible disk of 12", perfectly defined and round. Granting these objects to be equally distant from us with the stars, their real dimensions must be such as would fill, on the lowest computation, the whole orbit of Uranus. It is no less evident that, if they be solid bodies of a solar nature, the intrinsic splendor of their surfaces must be almost infinitely inferior to that of the sun's.
Page 199 - ... satellites. But we shall do wrong to judge of the fitness or unfitness of their condition from what we see around us, when, perhaps, the very combinations which convey to our minds only images of horror may be in reality theatres of the most striking and glorious displays of beneficent contrivance.
Page 259 - IN 1803, Sir William Herschel first determined and announced to the world, that there exist among the stars separate systems, composed of two stars revolving about each other in regular orbits. These he denominated binary stars, to distinguish them from other double stars where no such motion is detected, and whose proximity to each other may possibly arise from casual juxtaposition, or from one being in the range of the other.
Page 201 - These satellites offer remarkable, and indeed quite unexpected and unexampled peculiarities. Contrary to the unbroken analogy of the whole planetary system, the planes of their orbits are nearly perpendicular to the ecliptic, being inclined no less than 78° 58' to that plane, and in these orbits their motions are retrograde; that is, instead of advancing from west to east around their primary, as is the case with all the other planets and satellites, they move in the opposite direction. With this...
Page 227 - ... of their attraction beyond calculable limits. Under such circumstances, we might have " years of unequal length, and seasons of capricious temperature, planets and moons of portentous size and aspect, glaring and disappearing at uncertain intervals...
Page 195 - Fig. 46. broader and less strongly marked than those of Jupiter, and owing doubtless to a similar cause. That the ring is a solid opake substance, is shown by its throwing its shadow on the body of the planet on the side nearest the sun, and on the other side receiving that of the body.
Page 233 - Their tails consist of matter of such tenuity that the smallest stars are visible through them. They can only be regarded as great masses of thin vapor, susceptible of being penetrated through their whole substance by the sunbeams, and reflecting them alike from their interior parts and from their surfaces.
Page 174 - THIRD LAW. — The squares of the periodical times are as the cubes of the mean distances from the sun. The periodical time of a body is the time it takes to complete its orbit, in its revolution about the sun. Thus the earth's periodic time is one year, and that of the planet Jupiter about twelve years.
Page 256 - This remarkable law of variation appears strongly to suggest the revolution round it of some opaque body, which, when interposed between us and Algol, cuts off a large portion of its light. " It is,