2021年01月11日

Moon Phases in 2021
Video Credit:
Data: Lunar Reconnaissance Orbiter ; Animation: NASA’s Scientific Visualization Studio;
Music: Brandenburg Concerto No4-1 BWV1049 (Johann Sebastian Bach), by Kevin MacLeod via Incompetech

Explanation: What will the Moon phase be on your birthday this year? It is hard to predict because the Moon’s appearance changes nightly. As the Moon orbits the Earth, the half illuminated by the Sun first becomes increasingly visible, then decreasingly visible. The featured video animates images taken by NASA’s Moon-orbiting Lunar Reconnaissance Orbiter to show all 12 lunations that appear this year, 2021. A single lunation describes one full cycle of our Moon, including all of its phases. A full lunation takes about 29.5 days, just under a month (moon-th). As each lunation progresses, sunlight reflects from the Moon at different angles, and so illuminates different features differently. During all of this, of course, the Moon always keeps the same face toward the Earth. What is less apparent night-to-night is that the Moon’s apparent size changes slightly, and that a slight wobble called a libration occurs as the Moon progresses along its elliptical orbit.

APOD online webinar January 12: Free registration, hosted by Amateur Astronomers Association of New York.

Tomorrow’s picture: folklore sky


整个2021年的月相
影片提供:
数据提供: Lunar Reconnaissance Orbiter ; 动画: NASA’s Scientific Visualization Studio;
配乐:Brandenburg Concerto No4-1 BWV1049 (Johann Sebastian Bach), by Kevin MacLeod via Incompetech

说明: 今年你生日那天的月相会是什么?要预测其实有难度,因为每晚的月相都不同。随着月球绕行地球,受太阳光照射而半明半暗的月面,可见的日曜区先增后减。这部建构自美国航太总署.月球探勘号轨道船影像数据的主题影片,特别呈现2021年全部的12个月相周期。一个月相周期为期29.5天,略比一个月短,包含完整的月相变化循环。在一个月相周期里,随着时日递移,阳光从月表反射的角度会有变化,在视觉上月面的结构看来也会稍有不同。除此之外,月亮永远以同一面对着地球。而从前个夜晚到下一个,随着月亮沿着椭圆轨道运行,较不明显的是月亮的视小变化,以及称为天平动的月面晃动。

APOD在线网络研讨会1月12日: 免费注册,由纽约业余天文学家协会主办。

明日的图片: folklore sky

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