Combi M R, Mäkinen T, Bertaux J-L, Quémerais E, Ferron S, Coronel R
Dept. of Climate and Space Sciences and Engineering, University of Michigan, 2455 Hayward Street, Ann Arbor, MI 48109-2143.
Finnish Meteorological Institute, Box 503 SF-00101 Helsinki, FINLAND.
Planet Sci J. 2020 Dec;1(3). doi: 10.3847/psj/abb026. Epub 2020 Dec 4.
In 2017, 2018, and 2019, comets 46P/Wirtanen, 45P/Honda-Mrkos-Pajdusakova, and 41P/Tuttle-Giacobini-Kresak all had perihelion passages. Their hydrogen comae were observed by the Solar Wind ANisotropies (SWAN) all-sky hydrogen Lyman-alpha camera on the SOlar and Heliospheric Observer (SOHO) satellite: comet 46P for the fourth time and comets 45P and 41P for the third time each since 1997. Comet 46P/Wirtanen is one of a small class of so-called hyperactive comets whose gas production rates belie their small size. This comet was the original target comet of the Rosetta mission. The Solar Wind ANisotropies (SWAN) all-sky hydrogen Lyman-alpha camera on the SOlar and Heliospheric Observer (SOHO) satellite observed the hydrogen coma of comet 46P/Wirtanen during the apparitions of 1997, 2002, 2008, and 2018. Over the 22 years, the activity decreased and its variation with heliocentric distance has changed markedly in a way very similar to that of another hyperactive comet, 103P/Hartley 2. Comet 45P/Honda-Mrkos-Pajdusakova was observed by SWAN during its perihelion apparitions of 2001, 2011, and 2017. Over this time period the activity level has remained remarkably similar, with no long-term fading or abrupt decreases. Comet 41P/Tuttle-Giacobini-Kresak was observed by SWAN in its perihelion apparitions of 2001, 2006, and 2017 and has decreased in activity markedly over the same time period. In 1973 it was known for large outbursts, which continued during the 2001 (2 outbursts) and 2006 (1 outburst) apparitions. However, over the 2001 to 2017 time period covered by the SOHO/SWAN observations the water production rates have greatly decreased by factors of 10-30 over corresponding times during its orbit.
在2017年、2018年和2019年，46P/威斯特伦彗星、45P/本田-马尔科斯-帕德萨克ova彗星和41P/塔特尔-贾科比尼-克雷萨克彗星都经过了近日点。太阳和日球层观测台（SOHO）卫星上的太阳风各向异性（SWAN）全天氢莱曼α相机观测到了它们的氢彗发：46P彗星是自1997年以来第四次被观测到，45P彗星和41P彗星则是第三次被观测到。46P/威斯特伦彗星是一小类所谓的活跃彗星之一，其气体产生率与其小尺寸不符。这颗彗星是罗塞塔任务的原始目标彗星。太阳和日球层观测台（SOHO）卫星上的太阳风各向异性（SWAN）全天氢莱曼α相机在1997年、2002年、2008年和2018年的彗星出现期间观测到了46P/威斯特伦彗星的氢彗发。在这22年里，其活跃度下降，并且其随日心距离的变化与另一颗活跃彗星103P/哈特利2非常相似，发生了显著变化。45P/本田-马尔科斯-帕德萨克ova彗星在2001年、2011年和2017年的近日点出现期间被SWAN观测到。在此期间，其活动水平一直保持非常相似，没有长期衰减或突然下降。41P/塔特尔-贾科比尼-克雷萨克彗星在2001年、2006年和2017年的近日点出现期间被SWAN观测到，并且在同一时期其活动明显下降。1973年，它以大爆发而闻名，在2001年（2次爆发）和2006年（1次爆发）的出现期间爆发仍在继续。然而，在SOHO/SWAN观测覆盖的2001年至2017年期间，其水产生率在其轨道的相应时间内大幅下降了10至30倍。
