A little ramble through 19th century astronomy - spectra of comets

 

Nature January 8^th 1874

On the spectra of Comets

Here is a summary of comet spectra by H Vogel published in Poggendorffs Annalen

I will now give a summary of all the observations known to me of cometary spectra. 

1.      The first comet examined by spectrum analysis is the Comet I. 1864. Donati found its spectrum to consist of three bright bands, which (if one may judge from the figure in Astr Nachr No. 1488) do not  coincide with those of the hydrocarbon spectrum.

2.      Huggins and Secchi observed Temple’s Comet I. 1866, and got from it a weak continuous spectrum, in which Secchi saw three bright lines, Huggins only one. The line seen by both was the brightest, and situated in the middle between b and F of the solar spectrum; accordingly no coincidence with the hydrocarbon spectrum.

3.      In the spectrum of Comet II. 867, the continuous spectrum was relatively so strong that Huggins found it difficult to detect bright lines. “Once of twice”, he says “I suspected the presence of two or three bright lines, but of this observation I was not certain. The prismatic observation of this faint object, though imperfect, appears to show that this small comet is probably similar in physical structure to comet I.1866” In this case again probably no hydrocarbon.

4.      Brorsen’s Comet I. 1868 was observed by Huggins and Secchi. Both observed three zones of light; The middle one being the brightest, and lying in the green; while its brightest part was somewhat less refrangible than the brightest line of the air spectrum. From this observation, and the determination of the position of the other two faint bands, it appears that the comet spectrum was neither similar to that of nitrogen, nor to the hydrocarbon spectrum.

5.      Winnecke’s Comet II.1868, was also observed by Huggins and Secchi. The measurements and direct comparisons of Huggins gave an agreement of the cometary spectrum with that of carbon in olefiant gas. From Secchi’s measurements it appears that the sharply defined side of the middle band (towards the red end), nearly coincided with the line group b of the solar spectrum; at which part also the beginning of the middle band of the spectrum of hydrocarbon id situated.

6.      Comet I. 1870 was observed by Wolf and Rayet; the spectrum consisted of three bright bands, whose position, however, was not accurately determined.

7.      Comet I. 1870 was observed by Huggins and myself. Huggins found three bands, I only two. The measurements of the bands observed in common agree well; the spectrum appears to be identical with that of Brosen’s Comet.

8.      Comet III. 1871 (Encke) was observed by Huggins three days, by Young four and by myself six; it showed, as usual a spectrum of three bands. Huggins thought this agreed with the hydrocarbon spectrum ; while young and I observed no such coincidence.

9.      Comet IV. 1871 (Tuttle), examined only by me, gave a spectrum of three bands. Accurate measurements of their positions showed no coincidence with the hydrocarbon spectrum.

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