运动中：天王星和卫星
(原标题: In Motion: Uranus and Moons)
2021-11-30
浏览次数: 34
在天空中移动的是什么？有一颗行星因为太暗而无法用肉眼看到：天王星。本月早些时候，这颗经过土星的气态巨行星在接近冲日时被追踪到，当时它离地球最近，也是最亮的时候。这段由英国赫特福德郡贝福德伯里天文台拍摄的特色视频是一个四小时的延时拍摄视频，展示了天王星和它的四个最大的卫星：泰坦尼亚、奥伯龙、翁布里埃尔和阿里尔。天王星经过背景恒星的表观运动实际上是由地球围绕太阳的轨道运动所主导的。以天王星为中心的十字被称为衍射峰，它是由光在固定望远镜镜子的四个臂周围衍射而产生的。衍射峰的旋转不是由天王星的旋转引起的，而本质上是由地球的旋转引起的。在接下来的几个月里，人们可以用双筒望远镜看到天王星本身，但是，像往常一样，要看到它的卫星需要望远镜。
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What's that moving across the sky? A planet just a bit too faint to see with the unaided eye: Uranus. The gas giant out past Saturn was tracked earlier this month near opposition -- when it was closest to Earth and at its brightest. The featured video captured by the Bayfordbury Observatory in Hertfordshire, UK is a four-hour time-lapse showing Uranus with its four largest moons in tow: Titania, Oberon, Umbriel and Ariel. Uranus' apparent motion past background stars is really dominated by Earth's own orbital motion around our Sun. The cross seen centered on Uranus is called a diffraction spike and is caused by light diffracting around the four arms that hold one of the telescope's mirrors in place. The rotation of the diffraction spikes is not caused by the rotation of Uranus but, essentially, by the rotation of the Earth. During the next few months Uranus itself will be visible with binoculars, but, as always, to see its moons will require a telescope.