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An afterglow is a broad high arch of whitish or rosy light appearing in the sky due to very fine particles of dust suspended in the high regions of the atmosphere. An afterglow may appear above the highest clouds in the hour of deepening twilight, or reflected from the high snowfields in mountain regions long after sunset. The particles produce a scattering effect upon the component parts of white light. The true alpenglow, which occurs long after sunset or long before sunrise, is caused by the backscattering of red sunlight by aerosols and fine dust particles low in the atmosphere. It is an afterglow caused by direct illumination of atmospheric particles by sunlight as it refracts and gets scattered through the earth's atmosphere. The high-energy and high-frequency light is scattered out the most and the remaining low-energy, low-frequency reaches the observer in the horizon at twilight. The backscattering of this light further turns it pinkish-red. This period of time is referred to as the blue hour and is widely treasured by photographers and painters as it offers breathtaking imagery. The afterglow persists till the earth's shadow (terminator line) takes over the sky of the observer as nightfall and the stars appear, with planet Venus being the brightest star visible in the night sky just opposite to the Belt of Venus at the anti-solar point. After the eruption of the volcano Krakatoa in 1883, a remarkable series of red sunsets appeared worldwide. These were due to an enormous amount of exceedingly fine dust blown to a great height by the volcano's explosion, and then globally diffused by the high atmospheric currents. Edvard Munch's painting ''The Scream'' possibly depicts an afterglow during this period. Image:Lamma evening4.jpg|Sunset in Hong Kong after the 1991 eruption of Mount Pinatubo Image:dresden.afterglow.700px.jpg|An afterglow in Dresden, Saxony, Germany Image:Afterglow.jpg|An afterglow in Slovenian mountains, near Triglav Lakes Valley Image:Full_Image_Sunset_Bates College_Lewiston_Maine_July_3_2008_8.30PM.JPG|Sunset over the Bates College track in Lewiston, Maine. Image:Noarlunga Pier, Adelaide.jpg|An afterglow at a pier in Australia Image:Afterglow Kraków.JPG|An afterglow on Kraków's housing estate ==See also== * Belt of Venus * Earth's shadow * Gegenschein * Sunset * Red sky at morning 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Afterglow」の詳細全文を読む スポンサード リンク
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