Abstract
THE DOUBLE STAR 70 OPHIUCHI.—Of the numerous orbits which have been computed for this well-known double star, that derived by Dr. Schur in 1893 is perhaps entitled to greatest confidence. Nevertheless, even in the short interval which has since elapsed, Dr. See finds that the companion is several degrees in advance of the theoretical position based on Schur's orbit. In explanation of this, as well as of other departures from the orbit which appear on close investigation, Dr. See suggests that the companion is attended by a dark satellite, moving in a retrograde direction with a period of about thirty-six years, the period of the visible pair being a little less than ninety years. The distance of the companion from the centre of gravity of itself and satellite is probably about 0″˙3; and a circular orbit with node and inclination identical with the similar elements of the visible pair sufficiently explains the observed changes of position angle and distance. Adopting the parallax 0″˙2, the semi-axis major of the primary orbit is 22˙74 astronomical units, while that of the secondary orbit is 1˙5 astronomical units, and the combined mass is 1˙6 times that of the sun. The whole system of 70 Ophiuchi is thus contained in a space less than that occupied by the solar system; the orbit of the bright companion being intermediate in size between those of Uranus and Neptune, while the action of the dark satellite causes it to describe a secondary orbit corresponding in size with that of Mars (Astronomical Journal, No. 363).
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Our Astronomical Column. Nature 53, 305–306 (1896). https://doi.org/10.1038/053305a0
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DOI: https://doi.org/10.1038/053305a0