Abstract
MOTION AND MAGNITUDE—Students of elementary astronomy often believe that stellar motions in the line of sight soon produce changes in the magnitudes of stars. Motion towards the earth involves, of course, a certain increase of magnitude, and a motion of recession must carry with it a decrease, but the amount in the case of a star is far too small to be measurable, even if the magnitudes are observed during many generations. At the meeting of the Amsterdam Academy on November 24, Prof. Oudemans communicated the results of an investigation to determine exactly how long stars of which the velocity in the line of sight are known would have to go on moving, in order to produce a change of 0˙1 magnitude. From his own list of parallaxes in vol. 122 of the Astr. Nachrichten, and Vogel and Scheiner's list of proper motions in the line of sight (“Potsdam Observations,”vii. i. p. 153, 154), fourteen stars were selected, four of them receding from, and the remaining ten approaching, the solar system. Adopting a solar parallax=8″˙815, and the logarithm of the proportion of the increase of brilliancy for one magnitude=0.400, he found that the period required is given by the formula
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Our Astronomical Column. Nature 51, 160–161 (1894). https://doi.org/10.1038/051160a0
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DOI: https://doi.org/10.1038/051160a0