美国国家航空航天局NASA每日一图(天文)-2017年7月5日

2017 July 5

Aphelion Sunrise
Image Credit & Copyright: Stephen Mudge
Explanation: On July 3rd, planet Earth reached aphelion, the farthest point in its elliptical orbit around the Sun. Each year, this day of the most distant Sun happens to occur during winter in the southern hemisphere. That's where this aphelion sunrise from 2015 was captured in a time series composite against the skyline of Brisbane, Australia. Of course, seasons for our fair planet are not determined by distance to the Sun, but by the tilt of Earth's rotational axis with respect to the ecliptic, the plane of its orbit. Fondly known as the obliquity of the ecliptic, the angle of the tilt is about 23.4 degrees from perpendicular to the orbital plane. So the most distant sunrise occurs during northern summer, when the planet's north pole is tilted toward the Sun and the north enjoys longer, warmer days.

2017年7月5日

远日点日出图片来源与版权:斯蒂芬·麦基

解释:7月3日,地球到达远日点,在太阳周围的椭圆轨道最远点。每年,这一天最遥远的太阳在南半球冬季期间中发生。这就是2015年aphelion日出在澳大利亚布里斯班天际线的一个时间序列组合中被捕捉的。当然,我们美丽星球的季节并不是由距离太阳的距离决定的,而是地球自转轴相对于黄道的倾斜度,它的轨道的平面。被认为是黄道的倾角,倾斜的角度从垂直到轨道平面的角度大约为23.4度。因此,最遥远的日出发生在北方的夏季,当时行星的北极向太阳倾斜,而北方则是更长更温暖的日子。

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