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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