The Planar Arrangement of the Planetary System

Abstract

IN your issue of July 29 your reviewer devotes some space to my paper on the origin of the planetary system (Astronomische Nachrichten, No. 4308), and closes by asking, “Why, for instance, on the hypothesis of capture, are the vast majority of the orbits near the plane of the ecliptic and their motion direct?” This is because our system was formed by the unsymmetrical meeting of two streams of nebulosity or by the mere gravitational settling of a single nebula of curved and unsymmetrical figure, giving a rotating cosmical vortex, or spiral nebula, but without hydrostatic pressure as imagined by Laplace. In Lick Observatory Publications, vol. viii., Plate 38, you will find an illustration of H.V. 2 Virginis, a spiral nebula of unsymmetrical figure just beginning to coil up and form a system. What will happen in the later stages of this nebula is sufficiently shown in the Lick photographs of other nebulæ given in this volume. As the mass whirls and condenses under resistance, it will necessarily retain and draw down most of the nebulosity into the plane of motion. This is exactly what has given the planar arrangement of the bodies in the solar system. In Astronomische Nachrichten, Nos. 4341–2, your reviewer will find a fuller explanation of the method of capture, and other papers yet to come will make the theory so clear that it need not take up more of your valuable space at present.