Abstract
ABSOLUTE STELLAR MOTIONS.—Meddelande No. 65, from the Lunds Astronomical Observatory, gives an account of an important statistical study of the distribution of the absolute motions of a number of parallax stars which has been made by Mr. K. W. Gyllenberg. After excluding parallaxes smaller than 0·015″, there remain 160 stars for which absolute velocities can be determined. The components were calculated for an axis “Z” pointed to the galactic pole, an “H” axis in the plane of the Milky Way, whilst the third “Ξ” was directed towards the vertex found for 1470 stars with known radial velocities. The numerical work was curtailed by using Prof. Charlier's plan of dividing the sky into forty-eight compartments, and using the co-ordinates of the centres for the contained stars. Prof. Charlier's units Siriometer (1 Sm=106 dist. earth-sun) and Stellar-year (1 St. = 106 years) have been used (1 Sm/st. = 4.7375 km./sec.). After arranging the material according to type of spectrum, five star types, Ki (Arct.) to A2p (Cyg.) were excluded as having excessive velocities. The greatest mean velocities were found in the plane of the galaxy, the “Z” components giving the smallest mean value. The absolute velocities tend to increase as the parallax diminishes, but the increase is more rapid for the small parallaxes, probably due to the greater insecurity of these measures. Hence in the final stage of the work stars having parallaxes less than 0·025″ were excluded. It is concluded that the distribution of the absolute velocities for the remaining 144 stars is approximately represented by an ellipsoid of revolution flattened in the plane of the Milky Way, and, unlike the proper motions or radial velocities, the absolute motions show no principal vertex.
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Our Astronomical Column . Nature 96, 16–17 (1915). https://doi.org/10.1038/096016a0
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DOI: https://doi.org/10.1038/096016a0