Moon and Earth's thin atmosphere

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图注： Taken from the International Space Station (ISS), approximately 400 kilometers above the ground, the picture shows the Moon far in the background and Earth's thin atmosphere. It appears blue as light in this wavelength is scattered more than in others by the gases in the upper layers. The photo was taken in March 2015 by a crew member. Clearly visible is the vanishingly small layer of gases compared to Earth's dimensions. There is no clear border between the atmosphere and space; it is a smooth transition with no sharp edges. The thickness to the upper limit of the stratosphere, roughly 50 kilometers, does not even amount to one percent of Earth's radius. Above 600 kilometers, particles reaching the critical escape velocity can leave into space. The total mass of the atmosphere is around 300 times less than that of all oceans combined or one million times less than Earth's total mass.
来源： Earth Science and Remote Sensing Unit, NASA Johnson Space Center
来源链接

词汇表: 大气层
分类： 地球

授权许可： 公共领域 公共领域 图标

文件 ( 图像 3.99 MB)

Solar absorption lines

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图注： This is a high resolution spectrum of light from our Sun showing visible region of the electromagnetic spectrum. The absorption lines are visible clearly as narrow black regions. The visualization shown here was created to mimic a so-called echelle spectrum, with wavelength increasing from left to right along each strip, and from bottom to top. Each of the 50 horizontal strips covers 6 nanometers, for a complete spectrum across the visible range from 400 to 700 nanometers. This spectrum was created from a digital atlas observed with the Fourier Transform Spectrometer at the McMath-Pierce Solar Facility at the National Solar Observatory on Kitt Peak, near Tucson, Arizona (‘Solar Flux Atlas from 296 to 1300 nm" by Robert L. Kurucz, Ingemar Furenlid, James Brault, and Larry Testerman: National Solar Observatory Atlas No. 1, June 1984). Note: NSO/Kitt Peak FTS data used here were produced by NSF/NOAO.
来源： N.A. Sharp/KPNO/NOIRLab/NSO/NSF/AURA
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词汇表: 天体物理学 , 可见光谱 , 光谱线 , 吸收线

授权许可： 知识共享许可协议 署名 4.0 国际 (CC BY 4.0) 知识共享许可协议 署名 4.0 国际 (CC BY 4.0) 图标

文件 ( 图像 3.09 MB)

Close-up view of a sunspot

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图注： This image of a sunspot was taken by the Daniel K Inouye Solar Telescope (DKIST), operated by the U.S. National Science Foundation. It was taken only in light with a wavelength of 530 nanometers, within the greenish-yellow part of the visible spectrum. The picture reveals the detail of the spot's structure and the Sun’s photosphere. The dark central region, known as the umbra, is surrounded by a lighter area called the penumbra with radially elongated features stretching towards the umbra. Note that the umbra and penumbra here are not the same as the umbra and penumbra that occur during an eclipse. The sunspot measures approximately 5000 kilometres in diameter, roughly equivalent to the east-west span of China. While the umbra appears black, it is actually hot and bright. It only appears dark because it is a few thousand kelvin cooler than the surrounding solar photosphere. Surrounding the sunspot, granulation patterns of plasma are visible on the photospheric surface of the Sun.
来源： NSO/NSF/AURA
来源链接

词汇表: 光球 , 太阳 , 太阳黑子 , 米粒组织

授权许可： 知识共享许可协议 署名 4.0 国际 (CC BY 4.0) 知识共享许可协议 署名 4.0 国际 (CC BY 4.0) 图标

文件 ( 图像 5.23 MB)

Atmosphere of Venus

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图注： This image of Venus was captured in ultraviolet light by the Pioneer Venus Orbiter and highlights features of the planet’s thick atmosphere that are not visible in ordinary light. Venus has a dense, cloudy atmosphere composed mainly of carbon dioxide. In ultraviolet wavelengths, patterns in the upper cloud layers become visible, revealing swirling structures and bright and dark bands caused by differences in the composition and motion of the atmosphere. These ultraviolet features help scientists map wind patterns, atmospheric circulation, and cloud dynamics high above Venus’s surface. Unlike Earth’s atmosphere, which is relatively transparent in visible light, Venus’s atmosphere is so thick that no direct view of the surface is possible from space without special instruments. The extreme pressure and temperature near Venus’s surface are consequences of this dense gaseous envelope, making Venus a dramatic example of how different planetary atmospheres can be. This image demonstrates how observing a planet’s atmosphere in different wavelengths, such as ultraviolet, reveals details about its structure and behaviour.
来源： NASA
来源链接

词汇表: 大气层 , 金星

授权许可： 公共领域 公共领域 图标

文件 ( 图像 8.09 MB)

Conjunction of Mercury and Venus above the Moon

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图注： From the observing deck at the European Southern Observatory’s Paranal site in Chile, in March 2008, astronomers captured a conjunction of celestial objects—a moment when two or more astronomical objects appear close together in the sky as seen from Earth. In this scene, the innermost planets Mercury and Venus appear aligned above the Moon, forming a pattern against the sky just before dawn. Although they are at very different distances from Earth, the geometry of their orbits brought them into almost the same line of sight, creating this beautiful cosmic alignment. In the image, the bright crescent Moon is visible low in the sky near the horizon, forming the most prominent object in the lower part of the scene. Just above the Moon, the brighter planet Venus can be seen, while Mercury, fainter and further from the horizon, appears nearby in the upper part of the image.
来源： ESO/Y. Beletsky
来源链接

词汇表: 合

授权许可： 知识共享许可协议 署名 4.0 国际 (CC BY 4.0) 知识共享许可协议 署名 4.0 国际 (CC BY 4.0) 图标

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