A Circumhorizontal Arc Over Ohio

NASA中文 2019年5月19日下午5:502019年12月15日上午11:11

2019 May 19

A Circumhorizontal Arc Over Ohio
Image Credit & Copyright: Todd Sladoje

Explanation: Why would clouds appear to be different colors? The reason here is that ice crystals in distant cirrus clouds are acting like little floating prisms. Sometimes known as a fire rainbow for its flame-like appearance, a circumhorizon arc lies parallel to the horizon. For a circumhorizontal arc to be visible, the Sun must be at least 58 degrees high in a sky where cirrus clouds are present. Furthermore, the numerous, flat, hexagonal ice-crystals that compose the cirrus cloud must be aligned horizontally to properly refract sunlight in a collectively similar manner. Therefore, circumhorizontal arcs are quite unusual to see. This circumhorizon display was photographed through a polarized lens above Dublin, Ohio in 2009.

天文·每日一图

时间螺旋

作者Samuel Chan 2024年7月1日2024年7月2日

An illustrated spiral is shown depicting many significant events that have occurred since the big bang. The big bang is at the center, and a city built by humans is at the spiral’s end. Please see the explanation for more detailed information.
这张图所示的时间螺旋，呈现了其中的一些重要里程碑。螺旋的中心是大爆炸，人类建造的城市位于螺旋的末端。有关更多详细信息，请参阅说明。