Abstract
THE SYSTEM OF CASTOR.—A very interesting discovery with regard to this well-known binary star has been made by Dr. Belopolsky (Bull. Acad. Imp. Set. St. Petersbourg, vol. iv. No. 3). In addition to the two luminous bodies, which perform their revolution in a period of about 1000 years, Dr. Belopolsky's observations indicate that the brighter star, α1 Geminorum, has a dark companion very similar to that of Algol, except that it never produces eclipses. The existence of this dark body was suspected in 1894, and it was fully confirmed by photographs of the spectrum taken at Pulkowa early in the present year, showing periodic changes in the velocity of the star along the line of sight. Thirteen photographs were obtained, and from these the velocities of α1, Geminorum towards or away from the sun were deduced. Although the available data are insufficient for a complete determination of the orbit, it may be taken to be circular as a first approximation, and a period of revolution of 2˙98 days sufficiently accords with the spectroscopic measurements. The proper motion of the system of α1, is 1˙0 geographical mile (= 4˙6 English miles) per second away from the sun, while the relative orbital velocity is 4˙5 geographical miles (20˙7 English miles) per second.
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Our Astronomical Column. Nature 54, 63–64 (1896). https://doi.org/10.1038/054063b0
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DOI: https://doi.org/10.1038/054063b0