| Issue |
A&A
Volume 403, Number 1, May III 2003
|
|
|---|---|---|
| Page(s) | L7 - L10 | |
| Section | Letters | |
| DOI | https://doi.org/10.1051/0004-6361:20030414 | |
| Published online | 29 April 2003 | |
Letter to the Editor
The infrared spectrum of Neptune at 3.5–4.1 microns: Search for H
and evidence for recent meteorological
variations *
1
Max-Planck-Institut für extraterrestrische Physik, Postfach 1603, 85740 Garching, Germany
2
LESIA, Observatoire de Paris, 5 place Janssen, 92195 Meudon Cedex, France e-mail: Therese.Encrenaz@obspm.fr
Corresponding author: H. Feuchtgruber, fgb@mpe.mpg.de
Received:
24
February
2003
Accepted:
19
March
2003
The infrared spectrum of Neptune at 
m and
m has been measured at a spectral
resolution of 1200.
The observed flux is stronger by a factor ~3 compared to
previous measurements, suggesting important meteorological
variations between 1997 and 2002. The flux is detected mostly
from a bright belt at mid-southern latitudes. Strong
absorptions, identified as methane, are observed over
the L band. The observed 
spectrum can be fitted by a multilayer model assuming that
the solar light is partly reflected above several layers,
including the haze and stratospheric
photochemical hazes.
An upper limit to a disk averaged column density of
of
is
reported, consistent with present ionospheric models.
Key words: line: formation / radiative transfer / planets and satellites: individual: Neptune / infrared: solar system
© ESO, 2003
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