Our Astronomical Column

Abstract

SECULAR VARIATIONS OF THE INTERIOR PLANETS.—As far back as 1859, Leverrier discovered that the movement of the perihelion point of the orbit of Mercury was greater than could be accounted for by the action of all the known planets, and he attributed this to the effect of a group of unknown bodies circulating between the orbit of Mercury and the sun. Prof. Newcomb has recently gone over the ground again, and the results of his work are given in Comptes-rendus of December 10. A brief statement of the tentative conclusions arrived at was given in these columns on November 29 (p. 114). From a discussion of a vast number of observations he has re-determined the secular variations for the orbits of Mercury, Venus, the Earth, and Mars, and he has computed the masses of Mercury, Venus, and Jupiter from the periodical perturbations which they produce; the adopted value of the earth's mass is deduced from the parallax 8″˙80, and for Mars the adopted mass is that derived from observations of the satellites. It is then shown that with these masses the calculated values of the secular variations differ from the observed ones, the divergences being especially great in the movements of the perihelia of the orbits of Mercury and Mars, and of the node of Venus. Two explanations of the differences are open to us: (1) It may be supposed, as suggested by Prof. Asaph Hall, that the law of gravitational attraction is not strictly true, and that the attractive force of the sun varies inversely as the distance raised to the power of approximately 2˙000000 1574; (2) they may be attributed to the influence of unknown masses of matter.