期刊
PLANETARY SCIENCE JOURNAL
卷 2, 期 2, 页码 -出版社
IOP Publishing Ltd
DOI: 10.3847/PSJ/abdd3a
关键词
-
资金
- NASA Postdoctoral Program at the NASA Goddard Space Flight Center
- National Science Foundation [AST-1614471, 1616306, 2009398]
- Planetary Science Division Internal Scientist Funding Program through the Fundamental Laboratory Research (FLaRe) work package
- NASA Astrobiology Institute through the Goddard Center for Astrobiology [13-13NAI7-0032]
- NASA Planetary Astronomy/Solar System Observations Program [18-SSO18_2-0040, 80NSSC17K0705]
- National Aeronautics and Space Administration [NNH14CK55B]
- Direct For Mathematical & Physical Scien
- Division Of Astronomical Sciences [1616306, 2009398] Funding Source: National Science Foundation
The study detected CH3OH emission in comet 46P/Wirtanen using the Atacama Compact Array, revealing rapidly varying and anisotropic outgassing. The consistent blue offset of the line center suggests enhanced CH3OH sublimation from the sunward hemisphere of the comet, likely from icy grains. These results highlight the exceptional capabilities of the ACA for time-resolved measurements of comets like 46P/Wirtanen.
We report the detection of CH3OH emission in comet 46P/Wirtanen on UT 2018 December 8 and 9 using the Atacama Compact Array (ACA), part of the Atacama Large Millimeter/Submillimeter Array (ALMA). These interferometric measurements of CH3OH along with continuum emission from dust probed the inner coma (<2000 km from the nucleus) of 46P/Wirtanen approximately one week before its closest approach to Earth (Delta = 0.089-0.092 au), revealing rapidly varying and anisotropic CH3OH outgassing during five separate ACA executions between UT 23:57 December 7 and UT 04:55 December 9, with a clear progression in the spectral line profiles over a timescale of minutes. We present spectrally integrated flux maps, production rates, rotational temperatures, and spectral line profiles of CH3OH during each ACA execution. The variations in CH3OH outgassing are consistent with Wirtanen's 9 hr nucleus rotational period derived from optical and millimeter wavelength measurements and thus are likely coupled to the changing illumination of active sites on the nucleus. The consistent blue offset of the line center indicates enhanced CH3OH sublimation from the sunward hemisphere of the comet, perhaps from icy grains. These results demonstrate the exceptional capabilities of the ACA for time-resolved measurements of comets such as 46P/Wirtanen.
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