Journal Article

New limits on H<sup>+</sup><sub>3</sub> abundance on Neptune using Keck NIRSPEC

H. Melin, T. Stallard, S. Miller, M. B. Lystrup, L. M. Trafton, T. C. Booth and C. Rivers

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 410, issue 1, pages 641-644
Published in print January 2011 | ISSN: 0035-8711
Published online December 2010 | e-ISSN: 1365-2966 | DOI:
New limits on H+3 abundance on Neptune using Keck NIRSPEC

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Neptune and Uranus are observed with Keck II NIRSPEC in an attempt to detect H+3 emission from Neptune. In this set of observations, H+3 emission remains undetected at Neptune, whereas line-resolved emission from Uranus was observed with a signal-to-noise ratio of ∼100. Using this, we have derived an upper limit of the column-integrated H+3 density on Neptune of 1.5 (+4.8−0.9)× 1013 m−2, assuming a temperature of 550±100 K. This value improves the previous established limit by a factor of 20 and shows that the H+3 density predicted by the best available model overestimate the density by at least a factor of 3.

In addition, the solar reflection continuum of Neptune in the K and L′ bands is seen to be brighter on the Northern hemisphere by a factor of ∼2, whereas previous observations had noted the solar reflection as being brighter on the Southern hemisphere.

Keywords: techniques: spectroscopic; planets and satellites: atmospheres; planets and satellites: aurorae; planets and satellites: composition; planets and satellites: individual: Uranus; planets and satellites: individual: Neptune

Journal Article.  2941 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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