云层上方的极光

云层上方的极光

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2021年05月30日 Aurora over Clouds Image Credit & Copyright: Daniele Boffelli Explanation: Auroras usually occur high above the clouds. The auroral glow is created when fast-moving particles ejected from the Sun impact the Earth’s magnetosphere, from which charged particles spiral along the Earth’s magnetic field to strike atoms and molecules high in the Earth’s atmosphere. An oxygen atom, for example, will glow in the green light commonly emitted by an aurora after being energized by such a collision. The lowest part of an aurora will typically occur about 100 kilometers up, while most clouds exist only below about 10 kilometers. The relative heights of clouds and auroras are shown clearly in the featured picture in 2015 from Dyrholaey, Iceland. There, a determined astrophotographer withstood high winds…

船底AG的爆发云

船底AG的爆发云

ByNASA中文

2021年05月26日 The Outburst Clouds of Star AG Car Image Credit: NASA, ESA, STScI; Processing: Judy Schmidt; Text: Anders Nyholm Explanation: What created these unusual clouds? At the center of this 2021 Hubble image sits AG Carinae, a supergiant star located about 20,000 light-years away in the southern constellation Carina. The star’s emitted power is over a million times that of the Sun, making AG Carinae one of the most luminous stars in our Milky Way galaxy. AG Carinae and its neighbor Eta Carinae belong to the scarce Luminous Blue Variable (LBV) class of stars, known for their rare but violent eruptions. The nebula that surrounds AG Car is interpreted as a remnant of one or more such outbursts. This nebula measures 5 light-years across, is…

达多五石上空的火星

达多五石上空的火星

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2021年03月23日 Mars over Duddo Stone Circle Image Credit & Copyright: Ged Kivlehan Explanation: Why are these large stones here? One the more famous stone circles is the Duddo Five Stones of Northumberland, England. Set in the open near the top of a modest incline, a short hike across empty fields will bring you to unusual human -sized stones that are unlike anything surrounding them. The grooved, pitted, and deeply weathered surfaces of the soft sandstones are consistent with being placed about 4000 years ago — but placed for reasons now unknown. The featured image — a composite of two consecutive images taken from the same location — was captured last October under a starry sky when the Earth was passing near Mars, making the red…

朱诺号的木星景观

朱诺号的木星景观

ByNASA中文

2020年11月23日 A Jupiter Vista from Juno Image Credit: NASA/JPL-Caltech/SwRI/MSSS; Processing & License: Kevin M. Gill; Explanation: Why do colorful cloud bands encircle Jupiter? Jupiter’s top atmospheric layer is divided into light zones and dark belts that go all the way around the giant planet. It is high horizontal winds — in excess of 300 kilometers per hour — that cause the zones to spread out planet-wide. What causes these strong winds remains a topic of research. Replenished by upwelling gas, zonal bands are thought to include relatively opaque clouds of ammonia and water that block light from lower and darker atmospheric levels. One light-colored zone is shown in great detail in the featured vista taken by the robotic Juno spacecraft in 2017. Jupiter’s atmosphere is…