Abstract
Comets with large gas production offer a unique chance to observe a H2-flux of about 105 photon cm−2 s−1 sr−1 (1 Rayleigh) at wavelengths 8497.4 Å, 8560.2 Å and 8747.9 Å-i.e., where photon counting methods are still applicable. In the following it will be shown that population of the vibrational levels, giving rise to these quadrupole overtone transitions, is dominated by photodissociation of methane, and that the emission even of quadrupole lines is not attenuated by collisional quenching. Wavelength scanning by ±1 Å is shown to be enough to discriminate between cometary and atmospheric emissions by phase-sensitive subtraction techniques. Solid angle of Ω<10−7 sr has to be used, whence follows that a large ground-based telescope combined with a tilting Fabry-Perotfilter is best suited for detection of the near-infrared H2-emissions at reasonable counting rates and sufficient rejection of the atmospheric background.
Since H2 is supposed to be formed mainly by the photolysis of CH4, the optimum time for detection will be during approach to perihelion when, because of its high vapor pressure, methane will vaporize from the cometary nucleus. Variation of the source strength of both CH4 and its photolysis product H2 with time are particularly valuable indicators for the structure of the nucleus, its thermal history and conditions of formation. A high-resolution tilting filter photometer, which allows phase-sensitive background subtraction was used for the first time for near-infrared observations on the dust coma of Comet Kohoutek (Barbieriet al., 1974). The same technique was successfully used for the determination of an upper limit for CH4 production at 3.3 μ by airborne observations on the same comet (Cosmoviciet al., 1974).
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Barbieri, C., Cosmovici, B. C., Michel, K. W., Nishimura, T., and Roche, A.: 1974,Icarus 23, 568.
Bertaux, J. L., Blamont, J. E., and Festou, M.: 1973,Astron. Astrophys. 25, 415.
Biermann, L.: 1968, On the Emission of Atomic Hydrogen in Comets', JILA Report No. 93, University of Colorado, Boulder.
Biermann, L. and Trefftz, E.: 1964,Z. Astrophys. 59, 1.
Cartwright, D. and Drapatz, S.: 1970,Astron. Astrophys. 4, 443.
Chamberlain, J. W. and Roesler, F. L.: 1955,Astrophys. J. 121, 541.
Cosmovici, B. C., Drapatz, S., Michel, K. W., Roche, A., and Wells, W. C.: 1974,Mitt. Astron. Ges. 35, 250.
Donn, B.: 1963,Icarus 2, 396.
Fairbairn, A. R.: 1964,AIAA J. 2, 1004.
Feldman, P. D. and Fastie, W. G.: 1973,Astrophys. J. 185, L101.
Finson, M. L. and Probstein, R. F.: 1968,Astrophys. J. 154, 353.
Giese, R. M.: 1961,Z. Astrophys. 51, 119.
Gull, T. R., Harwit, M.: 1971,Astrophys. J. 168, 15.
Hall, L. A. and Hinteregger, H. E.: 1970,J. Geophys. Res. 75, 6959.
Hapke, B. W.: 1963,Geophys. Res. 68, 4571.
Hayakawa, S., Matsumoto, T., Mizuno, T., Nishimura, T., Okuda, H., and Sugimoto, D.: 1968,Icarus 9, 357.
Heaps, H. S. and Herzberg, G.: 1952,Z. Physik. 133, 48.
Herzberg, G.: 1966,Molecular Spectra and Molecular Structure, Vol. 3, 2nd Ed., Van Nostrand Reinhold Co., Cincinnati.
Hill, F. L. and Van Vleck, J. H.: 1948,Phys. Rev. 32, 250.
Hübner, W. F.: 1965,Z. Astrophys. 63, 22.
Joder, M. J.: 1972,J. Chem. Phys. 56, 3226.
Kaplan, S. A. and Pikel'ner, S. B.: 1970,The Interstellar Medium, Harvard University Press, Cambridge, Mass.
Keller, H. U.: 1973,Astron. Astrophys. 23, 269.
Kiefer, J. H. and Lutz, R. W.: 1971,Astrophys. J. 44, 668.
Krishna-Swamy, K. S.: 1971,Astrophys. J. 167, 63.
Mayer, P. and O'Dell, C. R.: 1968,Astrophys. J. 153, 951.
Michel, K. W.: 1973, ‘Zur IR-Emission von H2-Molekülen aus einer Kometen-Koma’, MPI-PAE/TB Extraterr. No. 8.
Michel, K. W. and Nishimura, T.: 1976, Proc. of the IAU Colloquium No. 31 on Interplanetary Dust and Zodiacal Light.
Minnaert, M., Mulders, G. F. W., and Houtgast, J.: 1940,Photometric Atlas of the Solar Spectrum, Sterrewacht Sonnenborgh, Utrecht.
Moore, C. E., Minnaert, M. G. J., and Houtgast, J.: 1966,The Solar Spectrum, National Bureau of Standards Monograph, 61.
O'Dell, C. R.: 1971,Astrophys. J. 164, 511.
Pearse, R. W. B. and Gaydon, A. G.: 1963,The Identification of Molecular Spectra, Chapman and Hall, London
Potter, A. E. and Del Duca, B.: 1964,Icarus 3, 103.
Rahe, J., Donn, B., and Wurm, K.: 1969,Atlas of Cometary Forms, NASA, SP-198.
Rao, K. N. and Weldon, C. W.: 1972,Molecular Spectroscopy, Academic Press, New York and London.
Roche, A., Cosmovici, B. C., Drapatz, S., Michel, K. W., and Wells, W. C.: 1975,Icarus 24, 120.
Shimazaki, T. and Laird, A. R.: 1970,J. Geophys. Res. 75, 3221.
Singer, S. F. and Bandermann, L. W.: 1967, ‘The Zodiacal Light and the Interplanetary Medium’, NASA SP-150.
Spitzer, L., Dressler, K., and Upson, W. L.: 1964,Publ. Astron. Soc. Pacific 76, 391.
Stief, L. J., Donn, B., Glicker, S., Gentieu, E. P., and Mentall, J. E.: 1972,Astrophys. J. 171, 21.
Swensson, J. W., Benedict, W. S., Delbouille, L., and Roland, G.: 1970, ‘The Solar Spectrum from λ 7498 to λ 12016’,Mem. Soc. Roy. Sci. Liège.
Swings, P.: 1965,Quart. J. Roy. Astron. Soc. 6, 28.
Swings, P. and Haser, L.: 1956,Atlas of Representative Cometary Spectra, Ceuterick Press, Louvain.
Wallace, L.: 1960,Astrophys. J. 132, 854.
Werner, M. W. and Harwit, M.: 1968,Astrophys. J. 154, 881.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Michel, K.W., Nishimura, T. & Cosmovici, C.B. On the possibility of H2-near-infrared detection in comets with large gas production. Astrophys Space Sci 40, 253–280 (1976). https://doi.org/10.1007/BF00640446
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00640446