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  • 标题:Thermal Emission from the Uranian Ring System
  • 本地全文:下载
  • 作者:Edward M. Molter ; Imke de Pater ; Michael T. Roman
  • 期刊名称:The Astronomical journal
  • 印刷版ISSN:0004-6256
  • 电子版ISSN:1538-3881
  • 出版年度:2019
  • 卷号:158
  • 期号:1
  • 页码:1-13
  • DOI:10.3847/1538-3881/ab258c
  • 语种:English
  • 出版社:American Institute of Physics
  • 摘要:The narrow main rings of Uranus are composed of almost exclusively centimeter- to meter-sized particles, with a very small or nonexistent dust component; however, the filling factor, composition, thickness, mass, and detailed particle size distribution of these rings remain poorly constrained. Using millimeter (1.3–3.1mm) imaging from the Atacama Large (sub-)Millimeter Array and mid-infrared (18.7 μm) imaging from the Very Large Telescope VISIR instrument, we observed the thermal component of the Uranian ring system for the first time. The ò ring is detected strongly and can be seen by eye in the images; the other main rings are visible in a radial (azimuthally averaged) profile at millimeter wavelengths. A simple thermal model similar to the Near-Earth Asteroid Thermal Model (NEATM) of near-Earth asteroids is applied to the ò ring to determine a ring particle temperature of 77.3±1.8 K. The observed temperature is higher than expected for fast-rotating ring particles viewed at our observing geometry, meaning that the data favor a model in which the thermal inertia of the ring particles is low and/or their rotation rate is slow. The ò ring displays a factor of 2–3 brightness difference between periapsis and apoapsis, with 49.1%±2.2% of sightlines through the ring striking a particle. These observations are consistent with optical and near-infrared reflected light observations, confirming the hypothesis that micron-sized dust is not present in the ring system.
  • 关键词:planetary systems;planets and satellites: rings
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