Abstract
RESEARCHES ON THE DIAMETER OF THE SUN.—In continuation of his investigations on the supposed changes in the sun's diameter from year to year (NATURE, vol. xxxv. p. 496), Prof. Auwers publishes in the Sitzungsberichte der Königlich Preussischen Akadeinie der Wissenschaften zu Berlin, 1887, No. xxviii., the result of his researches on the yearly inequality of the diameter. The existence of such an inequality has been pointed out by Lindenau in his discussion of Maskelyae's observations; by Cesaris, Carlini, and Rosa in the Milan observations; and by Struve in the Dorpat observations. More recently Rosa has discussed extensive series of Greenwich observations of the sun, and also Madras observations; New-comb and Holden have discussed Greenwich and Washington observations; and Hilfiker has discussed transits of the sun's diameter obtained at Neuchâtel. To these must now be added Prof. Auwers' careful discussion of the Greenwich transit-circle observations, both of horizontal and vertical diameter, obtained during the years 1851–83 inclusive, as well as of the extensive series of Washington and Oxford observations collected in his former paper, referred to above. These discussions all show the existence of apparent inequalities in the sun's diameter during the year, but do not appear to be at all conclusive as to the reality of such variations in the sun itself. In Prof. Auwers' opinion they are due to the effect of temperature on the instrument, or to the effect of difference in the telescopic image of the sun as observed at opposite seasons of the year. Thus a most remarkable inconsistency appears in the results obtained from the Greenwich observations, bolh of horizontal and vertical diameter, 1851–83, and from the Neuchâtel observations, of horizontal diameter only, for 1862–83. The following table shows the discordances from the mean for each month of the year for the two series:—
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Our Astronomical Column . Nature 36, 256–257 (1887). https://doi.org/10.1038/036256a0
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DOI: https://doi.org/10.1038/036256a0