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Neptune: Observations of the H2 Quadrupole Lines in the (4–0) Band

Published online by Cambridge University Press:  14 August 2015

L. Trafton
L. Trafton*
Affiliation:
McDonald Observatory and Dept. of Astronomy, University of Texas at Austin, Tex., U.S.A.

Abstract

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The first measurement of Neptune's quadrupole H2 lines is reported. The equivalent widths of the S(0) and S(1) lines of the (4–0) band are given along with the corresponding widths measured from comparison spectra of Uranus taken on the same nights. These are interpreted in terms of both an inhomogeneous atmosphere overlying a reflecting layer and a homogeneous, semi-infinite, scattering atmosphere. Only the scattering model proves to be consistent with Neptune's spectrum in this wavelength region. The H2 abundance along the scattering mean free path is found to be less than the value for Rayleigh scattering in pure H2. This result is interpreted in terms of the presence of H2, CH4 and at least one other gas, instead of the more conventional interpretation in terms of the presence of an aerosol mixed with H2. Weak features in the continuum were observed. Their widths and the strength of the H2 features indicate that H2 is more abundant than the sum of the remaining gases in these atmospheres.

Type
Part III Outer Planets and Their Satellites
Information
Symposium - International Astronomical Union , Volume 65: Exploration of the Planetary System , 1974 , pp. 497 - 511
Copyright
Copyright © Reidel 1974 

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