First Attempt at a Theory of the Arrangement and Motion of the Sidereal System. The Astrophysical Journal LV, [55], 1922, pp. 302-327 [FIRST USE OF THE TERM DARK MATTER]

Chicago: University of Chicago, 1922. 1st Edition. FIRST EDITION OF THE 1st APPEARANCE IN PRINT OF THE TERM "DARK MATTER" & FIRST SUGGESTION OF ITS EXISTENCE. This paper, First Attempt at a Theory of the Arrangement and Motion of the Sidereal System, represents a culmination of Kapteyn's life work and he died shortly before its publication. In it, he uses the term dark matter to denote invisible matter the existence of which is otherwise suggested by only by gravity. He further suggests that when his theory is perfected it may be possible to determine the amount of dark matter from its gravitational effect.

Jacobus Cornelius Kapteyn (1851-1922) was a Dutch astronomer who extensively studied the Milky Way and who discovered evidence of galactic rotation.

"In the beginning of the 20th century little was known about the overall structure of the Milky Way system... One unsolved problem was the possible existence of absorbing material near the plane of the Galaxy, which distorts distance estimates of stars... [When Kapteyn began his study of the problem] he used the latest observational data to compute a dynamical model of the Galaxy. To calculate the gravitational potential, the Galaxy was represented by 10 concentric ellipsoids of constant density and axial ratio 1/5.1. These ellipsoids were not related to any stellar population, and used only to express the changes of the mean density of the Galaxy. The Sun was placed near the centre of the Galaxy. Using kinematical data and star count Kapteyn was able to estimate the total spatial density of visible stars, as well as the total dynamical density. He noticed that these two quantities can differ due to the possible presence of some dark matter or faint stars.

Kapteyn wrote: "We therefore have the means of estimating the mass of dark matter in the universe. As matters stand at present it appears at once that this mass cannot be excessive" (Einasto, Dark Matter and Cosmic Web Story, 88). CONDITION & DETAILS: Chicago: University of Chicago Press. Complete. Ex-libris marking on the front flyleaf and pastedown. NO spine markings whatsoever. 4to (9.75 x 6.75 inches). [4], vi, [418], 4. Seven plates and in-text illustrations throughout. Tightly bound in red buckram. Gilt-lettered at the spine. Bright and clean throughout. Very good +.