ナショナルジオグラフィックさんのインスタグラム動画 - (ナショナルジオグラフィックInstagram)「Video by @babaktafreshi | A dozen notable meteor showers occur annually, and the Perseid meteor shower, which peaks around August 12-13 each year, is among the best. I usually set one of my more light-sensitive cameras with a fast wide-angle lens to film the brightest meteors, called fireballs. These are more luminous than Venus, which is the brightest object in the night sky after the moon. Most visible meteors are caused by particles that range in size from a small pebble to a grain of sand and weigh less than a gram or two. A meteor’s brilliant flash of light is caused not by mass but by high kinetic energy generated by speed. A fireball is produced by a larger, tennis ball-size meteoroid and may reach the ground in the form of a small rock, depending on its composition (ice, metal, or mineral). The 2023 Perseid meteor shower is expected to peak on the morning of August 13 in a moonless sky. It will be visible globally, but North America seems to be the prime location. Learn more about the night sky at @babaktafreshi.」8月9日 8時35分