来自英仙座的英仙流星群

探索宇宙（universe）！每天都会展示一张关于我们迷人宇宙的不同图像或照片，并附上一段由专业天文学家（astronomer）撰写的简短解释。

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

解释：今年是英仙流星群（Perseids meteor shower）观测条件良好的一年。一个关键原因是月球（Moon）没有照亮地球（Earth）的夜天（night sky），因此比往常能观测到更多的流星（meteor）。月球去哪了？它正忙着造访太阳。在英仙流星群达到峰值附近时，月球移动到了太阳的正前方，并在格陵兰岛和西班牙造成了一次日全食（total solar eclipse）。英仙流星群的发生是因为地球撞上了彗星（comet）Swift-Tuttle抛出的一股绕太阳运行的碎片流。尽管英仙流星群的流星通常只有沙粒大小，但它们往往速度快且明亮，因为Swift-Tuttle的碎片绕太阳运行的方向与地球的轨道运动（orbital motion）方向部分相反。在精选的图像合成中，这些图像是在捷克共和国的Jizerka经过几个夜晚积累而成的，英仙流星群的流星轨迹可以追溯到天空中的同一个位置——即它在英仙座（Perseus）的辐射点。

Explanation: This was a good year for the Perseids meteor shower. A key reason was the Moon was absent from lighting up Earth's night sky so that more meteors were visible than usual. Where was the Moon? It was busy visiting the Sun. Near the Perseids peak, the Moon moved directly in front of the Sun and created a total solar eclipse visible from Greenland and Spain. The Perseids occur when the Earth collides with a stream of Sun-orbiting debris cast off by Comet Swift-Tuttle. Perseid meteors, although typically only the size of a sand grain, tend to be fast and bright because Swift-Tuttle's debris orbits the Sun in a direction partly opposite Earth's orbital motion. In the featured image compilation, accumulated over several nights from Jizerka in the Czech Republic, the Perseids meteor streaks can be traced back to a single location on the sky -- its radiant in Perseus.