2024年3月14日

Moon Pi and Mountain Shadow

Image Credit & Copyright: Daniel Lopez (El Cielo de Canarias)

Explanation: What phase of the Moon is 3.14 radians from the Sun? The Full Moon, of course. Even though the Moon might look full for several days, the Moon is truly at its full phase when it is Pi radians (aka 180 degrees) from the Sun in ecliptic longitude. That’s opposite the Sun in planet Earth’s sky. Rising as the Sun set on March 9, 2020, only an hour or so after the moment of its full phase, this orange tinted and slightly flattened Moon still looked full. It was photographed opposite the setting Sun from Teide National Park on the Canary Island of Tenerife. Also opposite the setting Sun, seen from near the Teide volcano peak about 3,500 meters above sea level, is the mountain’s rising triangular shadow extending into Earth’s dense atmosphere. Below the distant ridge line on the left are the white telescope domes of Teide Observatory. Again Pi radians from the Sun, on March 25 the Full Moon will dim slightly as it glides through Earth’s outer shadow in a penumbral lunar eclipse.

Tomorrow’s picture: pixels in space

满月与山影

影像提供与版权: Daniel Lopez (El Cielo de Canarias)

说明: 离太阳3.14弧度的月相会是什么？当然是满月啰。即使月亮可能连续数天都看似满相，但真正的满月，只出现在月亮于黄道经度上与太阳相距π弧度（亦即180度）的时候。也就是说，在地球的天空中，月亮与太阳反向。在2020年3月9日那天，月亮于太阳西落时东升，离满相的瞬间仅过了一个小时左右，因此影像中这轮略扁的橙色月亮看起来仍是满相。在特内里费岛泰德国家公园内拍摄这张照片时，摄影者背对落日。而从约3,500米高的泰德火山顶附近看出去，与落日反向的，还有这座山峰升起并伸入地球浓密大气里的三角形影子。在左侧远方的棱线下方，可见到泰德天文台的白色圆顶。今年的3月25日，月亮会再次与太阳相距π弧度，届时会因月盘穿过地球的半影而发生半影月食，满月将稍微变暗。

明日的图片: pixels in space