Data for Neptune from occultation observations (original) (raw)
NASA/ADS
Abstract
Photoelectric observations of the occultation of BD- by Neptune on 1968 April 7 are analyzed. The observed occultation is produced by differential refraction of the starlight in Neptune's atmosphere, between about 400 and 500 km above the surface; at this height the molecular number density N , compared with AT 1020 at the base of the visible atmosphere. The atmospheric scale height is 28.9 + 2.6 (p.e.) km, so the ratio T/ of temperature to mean molecular weight is 38. The most likely atmospheric composition is then H2 with a few percent CH4. The occultation layer defines an oblate spheroid of equatorial radius 25265 + 36 (p.e.) km and axial ratio 0.9741 + 0.0051. If the atmosphere is strictly isothermal, the equatorial radius of the planetary body is then 24753 i 59 km. This corresponds to a mean density for Neptune of 1.666 + 0.013 g (which is close to the value for Uranus). Structure in the observed occultation curves suggests that the atmospheric temperature may increase inward; the mean density may then be larger than 1.666 g , but is very unlikely to exceed 1.77 g .
Publication:
The Astrophysical Journal
Pub Date:
May 1970
DOI:
Bibcode: