银河说-每日一图171205期：红蓝相间的天际

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红蓝相间的天际

该图片向我们展示什么呢？图片拍摄的地方过去曾是危地马拉的一片菠菜地，图片上不仅有葱绿的树木，还有一座巨大的火山volcánde火地岛(火火山)，火山顶部是赤热的熔岩。但是你可能会被图片左上方的蓝色圆圈吸引。该圆圈里面是月亮，它与圈内其他颜色部分合称为月华。月华是一种衍射现象，当光通过与其波长相近的小水滴时，就会出现光的强弱相间分布的情况，这就是衍射。云层的右边有一个缺口，我们可以看到一些恒星，甚至是距火山特别远的土星。尽管该火山经常有轻微火山喷发，该天体摄影师认为，在九月底火山大爆发期间能够拍摄到这个场景还是很幸运的。

译：银河说翻译组 Lee

A Horizon with Blue and Red
Image Credit & Copyright: Sergio Montúfar (Planetario Ciudad de La Plata)

Explanation: What's happening on the horizon? The horizon itself, past a spinach field in Guatemala, shows not only trees but a large volcano: the Volcán de Fuego(Volcano of Fire). The red glow at the top of the volcano is hot lava. But your eye may also be drawn to the blue circle above the horizon on the left. This circle surrounds the Moon and, together with other colors, is called a corona. A corona is caused by diffraction of light -- here moonlight -- by small water droplets in theEarth's intervening atmosphere. A break in the clouds on the right shows stars and even the planet Saturn far beyond the volcano. Although Volcán de Fuego frequently undergoes low-level activity, the astrophotographer considered himself lucky to capture the scene just during an explosive eruption in late September.

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也算异景了。