The Jupiter-family comet (JFC) 46P/Wirtanen passed the Earth at a distance of 0.077 au on 2018 December 16 UT, presenting a rare opportunity to study the chemical structure of its coma. With the James Clerk Maxwell Telescope we achieved a resolution of 800 km, which is smaller than the scale lengths of some distributed cometary molecules at the comet’s heliocentric distance of 1 au. Spectroscopic observations of the J = 4 − 3 transition of HCN showed generally uniform levels of outgassing activity during the observing period, 2018 December 14–20. Gas expansion velocities were ∼0.6 km s −1 , and the derived average HCN production rate was 7.4 × 10 24 mol s −1 . HCN and CH 3 OH emissions were detected at least 30″ (1600 km) from the nucleus, and the abundances of these species were typical for a JFC. The radial distribution of CH 3 OH is consistent with an extended source of sublimation such as a population of icy grains—cometar...

中文翻译：

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詹姆斯·克莱克·麦克斯韦（James Clerk Maxwell）望远镜对46P / Wirtanen彗星的光谱和连续谱成像

木星家族彗星（JFC）46P / Wirtanen在UT于2018年12月16日以0.077 au的距离通过地球，为研究其昏迷的化学结构提供了难得的机会。使用James Clerk Maxwell望远镜，我们获得了800 km的分辨率，该分辨率小于彗星的日心距为1 au时一些分布式彗星分子的尺度长度。HCN的J = 4-3跃迁的光谱观察表明，在观测期间（2018年12月14日至20日），除气活性总体上保持一致。气体膨胀速度为〜0.6 km s -1，得出的HCN平均产生率为7.4×10 24 mol s -1。在距核至少30英寸（1600公里）处检测到HCN和CH 3 OH排放，而这些物种的丰度是JFC的典型特征。