Abstract
THE COMPANION OF SIRIUS.—Prof. Eddington announced, at a recent lecture to the Cambridge Philosophical Society and the members of the Inter national Astronomical Union, an interesting result arrived at by Dr. C. E. St. John at Mount Wilson Observatory. It has been found possible to photo graph with the ioo-inch reflector the spectrum of the companion of Sirius separately from that of the bright star. It is of type F and therefore its surface brightness is greater than that of the sun; from its very feeble luminosity its diameter is concluded to be about that of the planet Uranus, while its mass is three-quarters of that of the sun. Hence its density is enormously great, and it is a favourable object for Einsteins third astronomical test—that of the spectral shift. Single stars do not avail for determining this, since we cannot separate radial velocity from Einstein shift. But in this case, differential measures from Sirius are possible, the correction for orbital motion being well known.
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Our Astronomical Column. Nature 116, 219 (1925). https://doi.org/10.1038/116219a0
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DOI: https://doi.org/10.1038/116219a0