OUR ASTRONOMICAL COLUMN

Abstract

THE SATELLITES OF MARS.—The results of the complete reduction and discussion of the Washington observations of the satellites of Mars, undertaken by their discoverer, Prof. Asaph Hall, have just been published by the United States Naval Observatory. The observations of the outer satellite Deimos extend from 1877, August 11, to October 31, and those of the inner one, Phobos, from August 17 to October 15. On November 7 and 12 the satellites were looked for, but could not be seen. In treating these observations with the view to the determination of the most probable orbital elements of the satellites, Prof. Hall assumes in the first place that their paths are circular, and by a graphical projection finds the angle between the orbit-plane and the plane perpendicular to the line of sight, as well as the angle of position of the major axis of the ellipse into which the circular path is projected. The resulting elements are then compared with the observations, and elliptical elements deduced from the resulting differences between calculation and observation, both for position and distance, by means of equations of condition. Thus the following values of the elliptical elements have been obtained from the Washington observations alone:—