Near-infrared Brightness of Ganymede and Callisto Eclipsed in Jovian Shadow: A New Scope to Investigate Jovian Upper Atmosphere
Near-infrared Brightness of Ganymede and Callisto Eclipsed in Jovian Shadow: A New Scope to Investigate Jovian Upper Atmosphere
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木卫三和木卫四的近红外亮度在木星阴影中黯然失色：研究木星高层大气的新视野
DOI：
10.1088/0004-637x/789/2/122
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发表时间：
2014
影响因子：
4.9
通讯作者：
and Takehiko Wada
中科院分区：
文献类型：
--
作者：
Kohji Tsumura;Ko Arimatsu;Eiichi Egami;Yutaka Hayano;Chikatoshi Honda;Jun Kimura;Kiyoshi Kuramoto;Shuji Matsuura;Yosuke Minowa;Kensuke Nakajima;Taishi Nakamoto;Mai Shirahata;Jason Surace;Yasuto Takahashi;and Takehiko Wada
根据哈勃太空望远镜和斯巴鲁望远镜的观测，我们发现木卫二，木卫三和木卫四即使没有直接被太阳光照射，也在1.5 μm左右明亮。观测是在视场外对木星进行非恒星跟踪，以减少由于木星非常接近而导致的杂散光扣除不确定性。它们的食光度是其未食亮度的10− 6-10− 7，这是足够低的，这种现象直到现在还没有被发现。此外，在1.5 μm处，日食中的欧罗巴小于其他欧罗巴的1/10，这是一个潜在的线索，可以解释光度的来源。同样地，斯皮策太空望远镜尝试在3.6 μm处观测木卫三，但没有被探测到，这表明它有很大的波长依赖性。目前还不清楚为什么它们即使在木星的阴影中也会发光，但木星高层大气中的薄雾向前散射的阳光被认为是最合理的候选者。如果是这样的话，这些伽利略卫星的观测，而被木星阴影黯然失色，为我们提供了一个新的技术来调查木星的大气成分。用这种方法研究木星的透射光谱，对于用凌日光谱研究太阳系外巨行星的大气具有重要意义。
Based on observations from the Hubble Space Telescope and the Subaru Telescope, we have discovered that Europa, Ganymede, and Callisto are bright around 1.5 μm even when not directly lit by sunlight. The observations were conducted with non-sidereal tracking on Jupiter outside of the field of view to reduce the stray light subtraction uncertainty due to the close proximity of Jupiter. Their eclipsed luminosity was 10− 6–10− 7 of their uneclipsed brightness, which is low enough that this phenomenon has been undiscovered until now. In addition, Europa in eclipse was< 1/10 of the others at 1.5 μm, a potential clue to the origin of the source of luminosity. Likewise, Ganymede observations were attempted at 3.6 μm by the Spitzer Space Telescope, but it was not detected, suggesting a significant wavelength dependence. It is still unknown why they are luminous even when in the Jovian shadow, but forward-scattered sunlight by hazes in the Jovian upper atmosphere is proposed as the most plausible candidate. If this is the case, observations of these Galilean satellites while eclipsed by the Jovian shadow provide us with a new technique to investigate the Jovian atmospheric composition. Investigating the transmission spectrum of Jupiter by this method is important for investigating the atmosphere of extrasolar giant planets by transit spectroscopy.