Reference : The Spectrum of Comet Bester (1947k).
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Physical, chemical, mathematical & earth Sciences : Space science, astronomy & astrophysics
The Spectrum of Comet Bester (1947k).
Swings, Polydore [Université de Liège - ULiège > Institut d'Astrophysique de Liège > > > >]
Page, Thornton [Mc Donald and Yerkes Observatories > > > > >]
Astrophysical Journal
University of Chicago Press
[en] An extensive program of observations, planned in advance, was carried out during the predicted return of Comet Bester in March and April, 1948, as the comet receded from heliocentric distance 0.8 A.U. to 1.55 A.U. The eighteen spectra obtained extend over various parts of the observable region from λ 3070 to λ 8760, most of them from λ 3500 to λ 6800 on grating dispersion. These, together with seventeen direct photographs, provide virtually a continuous record of changes in the comet during the observing period. Since the slit of the spectrograph was oriented along the tail, extending about 4.5 minutes of arc from the nucleus, our spectrograms record the extent of the various molecular bands away from the nucleus.
Based on this material and on observations of other comets, the following topics are discussed:
a) Variations with heliocentric distance, r.-In Comet Bester the ratios CN/C2, λ 4050/CH, λ 4050/CN, λ 4050/C2 and probably OH/NH all increase regularly with increasing r. No flares or sudden changes in spectrum were observed.
b) Extent of bands from the nucleus.-CO+, N2+, λλ 3378, 3509, and 3674 are found exclusively in the tail; CN, C2, NH, OH, λ 4050, and NH2 follow in order of decreasing extent from the nucleus.
c) The far ultraviolet region.-The ratio OH/NH varies from comet to comet, being somewhat less than unity for Comet Bester, greater than unity for Comet 1941d, and much less for 1947n and 1941c, which are in other respects comparable. In Comet Bester the OH bands have a peculiar rotational distribution, probably due to the fluorescence mechanism.
d) The photographic regions.-Twenty lines in the "λ 4050 group" behave in Comet Bester as if they originate from one molecular species.
e) The red and infrared regions.-The existence of bands (tentatively identified with the "red system" of CN) at λ 7906 is confirmed, and other bands of the "red system" at shorter wave lengths tentatively identified. A number of other faint maxima between λ 7000 and λ 8700 are noted.
f) The spectrum of the tail.-Nine bands of the CO+ "comet-tail system" are recorded, the (3, 0) band being abnormally strong. Four bands of the "Baldet-Johnson system" of CO+ are observed. Tentative identifications of the "β system" of NO and the "Schumann-Runge system" of O2 are noted. The strong emissions at λλ 3378, 3509, and 3674 are identified with CO2+, the third ionized molecule to be identified in comet tails.
A summary of identifications and conclusions is given at the end of the paper.
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