OCCULTATION DETERMINATION OF NEPTUNE'S OBLATENESS AND STRATOSPHERIC METHANE MIXING RATIO.

E. Lellouch, William B. Hubbard, B. Sicardy, F. Vilas, P. Bouchet

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Abstract

The occultation of a star by Neptune on 20 August 1985 was observed at 2. 2 mu m wavelength with telescopes at the European Southern Observatory (ESO) and the Cerro Tololo Inter-American Observatory (CTIO). The detection of a 'central flash' midway between immersion and emersion has allowed the determination of Neptune's oblateness, epsilon , and the atmospheric extinction at 2. 2 mu m, which is related to the stratospheric methane mixing ratio. It is found that epsilon equals (2. 08// minus //0//. //1//8** plus **0**. **1**9) multiplied by 10** minus **2 and, assuming a stratospheric temperature of 120 K, a value of 0. 6% (with an uncertainty of a factor of 10) is inferred for the methane mixing ratio (CH//4/H//2) at 0. 3 mbar. The latter value may indicate supersaturation of methane in Neptune's stratosphere.

Original languageEnglish (US)
Pages (from-to)227-231
Number of pages5
JournalNature
Volume324
Issue number6094
StatePublished - Jan 1 1986

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Neptune (planet)
occultation
mixing ratios
methane
stratosphere
supersaturation
European Southern Observatory
submerging
flash
observatories
extinction
telescopes
methylidyne
stars
wavelengths
temperature

ASJC Scopus subject areas

  • General

Cite this

Lellouch, E., Hubbard, W. B., Sicardy, B., Vilas, F., & Bouchet, P. (1986). OCCULTATION DETERMINATION OF NEPTUNE'S OBLATENESS AND STRATOSPHERIC METHANE MIXING RATIO. Nature, 324(6094), 227-231.

OCCULTATION DETERMINATION OF NEPTUNE'S OBLATENESS AND STRATOSPHERIC METHANE MIXING RATIO. / Lellouch, E.; Hubbard, William B.; Sicardy, B.; Vilas, F.; Bouchet, P.

In: Nature, Vol. 324, No. 6094, 01.01.1986, p. 227-231.

Research output: Contribution to journalArticle

Lellouch, E, Hubbard, WB, Sicardy, B, Vilas, F & Bouchet, P 1986, 'OCCULTATION DETERMINATION OF NEPTUNE'S OBLATENESS AND STRATOSPHERIC METHANE MIXING RATIO.', Nature, vol. 324, no. 6094, pp. 227-231.
Lellouch E, Hubbard WB, Sicardy B, Vilas F, Bouchet P. OCCULTATION DETERMINATION OF NEPTUNE'S OBLATENESS AND STRATOSPHERIC METHANE MIXING RATIO. Nature. 1986 Jan 1;324(6094):227-231.
Lellouch, E. ; Hubbard, William B. ; Sicardy, B. ; Vilas, F. ; Bouchet, P. / OCCULTATION DETERMINATION OF NEPTUNE'S OBLATENESS AND STRATOSPHERIC METHANE MIXING RATIO. In: Nature. 1986 ; Vol. 324, No. 6094. pp. 227-231.
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abstract = "The occultation of a star by Neptune on 20 August 1985 was observed at 2. 2 mu m wavelength with telescopes at the European Southern Observatory (ESO) and the Cerro Tololo Inter-American Observatory (CTIO). The detection of a 'central flash' midway between immersion and emersion has allowed the determination of Neptune's oblateness, epsilon , and the atmospheric extinction at 2. 2 mu m, which is related to the stratospheric methane mixing ratio. It is found that epsilon equals (2. 08// minus //0//. //1//8** plus **0**. **1**9) multiplied by 10** minus **2 and, assuming a stratospheric temperature of 120 K, a value of 0. 6{\%} (with an uncertainty of a factor of 10) is inferred for the methane mixing ratio (CH//4/H//2) at 0. 3 mbar. The latter value may indicate supersaturation of methane in Neptune's stratosphere.",
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