Astronomy for the use of schools and academies (1882) (14577652450)

Identifier: astronomyforuseo00gill (find matches)

Title: Astronomy for the use of schools and academies

Year: 1882 (1880s)

Authors: Gillet, J. A. (Joseph Anthony), 1837-1908 Rolfe, W. J. (William James), 1827-1910

Subjects: Astronomy

Publisher: New York : Potter, Ainsworth, & Co.

Contributing Library: The Library of Congress

Digitizing Sponsor: The Library of Congress

Text Appearing Before Image:

Fig. 318. portions of the orbit, the comet is invisible. Now it is impos- 284 ASTRONOMY. sible to distinguish the form of the visible portion in thetwo orbits. The same would be true were one of the orbitsa hyperbola. Whether a comet will describe an ellipse, a parabola, or ahyperbola, can be determined only by its velocity, taken in con-nection with its distance from the sun. Were a comet ninety-two and a half million miles from the sun, moving away fromthe sun at the rate of twenty-six miles a second, it would havejust the velocity necessary to describe a paiabola. Were itmoving with a greater velocity, it would necessarilv describe

Text Appearing After Image:

Fig. 319. a hyperbola, and, with a less velocity, an ellipse. So, at anydistance from the sun, there is a certain velocity which wouldcause a comet to describe a parabola; while a greater velocitywould cause it to describe a hyperbola, and a less velocity todescribe an ellipse. If the comet is moving in an ellipse, theless its velocity, the less the eccentricity of its orbit: hence, inorder to determine the form of the orbit of any comet, it isonly necessary to ascertain its distance from the sun, and itsvelocity at any given time. ASTRONOMY. 285

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1882

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