When a new comet has been discovered and its elements have been ascertained, it is usual for some astronomer, specially interested in the particular comet, to provide a table of predicted places for the comet many days or weeks in advance. Such a table is called an "ephemeris" and will enable other astronomers to know where to look for the new body, and, finding it, to obtain observations
Fig. 94.
THE CONSTRUCTION OF AN ELLIPSE.
which will be available for improving the accuracy of the elements first circulated.[1]
The significance of the various sections of a cone which constitute the different forms of orbit affected by comets is well and tersely stated by Howe[2] in the following extract:—"Suppose that a small body is at a very great distance from the Sun, and both bodies are motionless. The body will begin to fall toward the Sun, its path being
- ↑ Instructions how to compute an ephemeris for a comet after the elements have been ascertained will be found in Popular Astronomy, vol. ix, p. 311. June and July 1901.
- ↑ H. A. Howe, Elements of Descriptive Astronomy, New York, 1897, p. 189.
der Kometen und Planeten, 2nd ed., 2 vols. 8vo, Leipzig, 1882. A French translation by a Belgian, M. E. Pasquier, was published at Paris, 1886, under the title of Traité de la détermination des orbites des comètes el des planètes. See also a paper by Airy, in Memoirs R.A.S., vol. xi, p. 181. 1840.
