Stellar Motions; With Special Reference to Motions Determined by Means of the Spectrograph
William Wallace Campbell
Paperback
(RareBooksClub.com, March 5, 2012)
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1913 Excerpt: ... reference to lines drawn from the separate stars to the assumed vertices of the two streams. The proper motions whose directions make small angles with the lines through the vertices are most numerous, and as the deviations from these directions increase more and more the number of corresponding stellar motions decreases almost continuously. Calling the speed of the solar system unity, Dyson's investigation led him to the conclusion that the relative speed of the two streams is 2.6; that is, for a solar speed of 19 km. per second, the separation-speed of the streams would be 48 km. per second. Schwarzschild, of Gottingen, introduced a promising hypothesis in connection with this problem. There is a fair chance that it has greater probability of conforming to the reality. He leaves the stars in one system instead of dividing them into two streams, or drifts, and assumes that the components of the real stellar motions are on the average greater in one direction than in any other; and that the actual stellar motions, as functions of their directions, can be represented in amount and in direction by all the radii of an ellipsoid whose longest axis coincides with the direction of relative motion in Kapteyn's two-stream theory. Assuming this hypothesis to be correct, and that our solar system is travelling through the stellar system not at right angles to the long axis of the ellipsoid, we should have another representation of the preferences of the observed proper motions for the two directions which Kapteyn had determined. The difference between Kapteyn's and Schwarzschild's hypotheses may be more apparent than real. So far as we can now see, two streams of stars, thoroughly intermingled, with preferential motions in opposite directions, are essentially equiva...