A little ramble through 19th century astronomy - Struve's companion of Procyon 1873

 Nature March 23rd  1876

Struve’s Companion of Procyon

Mr Otto Struve, in his remarks at the Royal Astronomical Society, in May 1874, upon the later Pulkowa observations of the faint companion to Procyon, which he discovered on March 19 1873, and which has been supposed to account for the anomalous motions of the latter, established by the researches of Prof Auwers, referred to the circumstances of the small star not having been up to that time perceived with the 26 inch refractor of the Washington Observatory.

Admiral Davis, the present superintendent of this establishment, has communicated to the Astronomische Nachrichten, the particulars of observations principally instituted for the purpose of confirming the existence of Struve’s companion. The observations were commenced in November 1873 and have been continued to the beginning of the present year.

On no single occasion have Professors Newcomb and Holden, the usual observers, or anyone who has examined the star with the 26 inch refractor, been able to detect a companion in the position assigned by the Pulkowa measures. Close faint stars have, however been remarked in other position angles.

How then is the contradictory character of the Pulkowa and Washington observations to be accounted for? It can hardly be, as suggested by Mr Struve, that “ The surpassing brilliancy of the principal star may have hindered the recognition of the small companion in its neighbourhood”, since notwithstanding it does not appear that a smaller aperture than 22 inches was employed during the Washington observations, three closer companions were considered to be certainly in existence. There remains the supposition of variability of light of the Pulkowa companion, if differences of atmospheric circumstances be ignored as inadequate to explain the want of success of other observers detecting it. 

Nothing more is heard of the Smythian orange tinged eighth magnitude distant from Procyon in 1833. As is well known, the only observation confirmatory of the existence of this star is that of Mr Fletcher MP early in March 1850, unfortunately the distance was not measured, because there is a star of similar brightness on very nearly the same angle, but a distance of 330” measured by Capt. Jacob, Mr Powell and the late Lord Wrottesley. Anyone, however, who reads Mr Fletcher's letter to Admiral Smythe, printed in “sideral Chromatics” p.69, will se that there is little doubt the object observed in 1850 was the same that was measured, or rather estimated, as to position in 1833, the difference of distance not admitting of a mistake on the part of the experienced and careful astronomer.  The more distant star was judged to be blue by Mr Powell; the orange tinge recorded in the “the cycle” is a characteristic of a large number of known variable stars.

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