A little ramble through 19th century astronomy - The star Procyon in 1874

 Academy Newspaper Saturday 16^th May 1874

 

The Russian astronomer, M. Struve, who has come over to this country to make the final arrangements for the Transit of Venus in concert with Sir George Airy, communicated to the Astronomical Society, at their last meeting, a paper on the companion to Procyon, discovered by himself last year, Procyon, like Sirius, is distinguished by having an irregular proper  motion, by virtue of which it appears to describe an elliptic orbit about a central body, which, till M. Struve's discovery, had escaped detection. In an elaborate paper, Auwers showed that M. Struve's faint, but not necessarily small, star would satisfy the conditions required for the disturbing body, though the evidence of its being the missing member of the twin system was not conclusive; he pointed out, however, that if it were the vera causa, it would change its direction with reference to Procyon by some 9°, and Struve now finds that it has actually done this, so that this interesting point appears now to be settled satisfactorily. Strange to say, this companion has not been seen with any of the monster telescopes of this country or America, but Mr. Talmage stated at the meeting that he had measured its position with Mr. Barclay's telescope of nine inches aperture, at Leyton. The brightness of the principal star  is so overpowering that special contrivances are required to hide its light, and, as M. Struve pointed out, no amount of aperture in the instrument employed will make up for neglect of these precautions. Assuming a parallax of a quarter of a second of arc for Procyon, corresponding to a distance which light would take thirteen years to traverse, it would appear from Auwers’ investigation that Procyon must have a mass about eighty times that of our Sun, whilst its apparently minute companion would have one of seven times; but it should be remembered that the data on which these conclusions are founded are somewhat uncertain, and that considerable corrections may be required.

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