Abstract
URANUS AND ITS SATELLITES.—As part of his work at Mount Hamilton during 1894 and 1895, Prof. Barnard took up the measurement of the positions of the four moons of the planet Uranus, and his results have just been published (Astronomical Journal, No. 370). Even with the 36-inch telescope the two inner satellites were usually difficult objects, while Titania and Oberon were also difficult if there was any wind to disturb the telescope. Ariel seems to be generally about half a magnitude brighter than Umbriel, and is the more easily visible notwithstanding that it is nearer to the planet. The compared brightnesses of Titania and Oberon seemed at first to show a variation of their relative light, amounting to a whole magnitude, but it is by no means certain that a real change occurs in the brightness of either; a consideration of the circumstances under which the comparisons were made has led Prof. Barnard to the curious conclusion that his eye has a tendency to make the lower of two equal lights appear the brighter, and he therefore thinks it probable that the two outer satellites are of constant and nearly equal brightness.
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Our Astronomical Column. Nature 53, 587 (1896). https://doi.org/10.1038/053587a0
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DOI: https://doi.org/10.1038/053587a0