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木星“腰带”为何频繁玩失踪？[文章版权 禁止转载:考试与评价 http://www.trgroup.com.cn/te/ @h7jZ[7aAB0i# NFroG]
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太阳系里最大行星木星的表面通常都有两条暗色的“腰带”，南北半球各一条，但人们前一阵发现，木星南半球的带子消失了，而且这种现象隔10多年就会来一次，科学家对此也感到很困惑。
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去年，木星躲到太阳背后之前还挂着两条带，然而3个月后，当木星重新露脸时，人们却惊奇地发现它的“腰带”少了一条。
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木星两条“腰带”被称为南北赤道带。大概每隔10到15年，其中的一条带子就会消失或重现，而具体原因至今还是个谜。
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Jupiter loses one of its stripes and scientists are stumped as to why
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Jupiter has lost one of its iconic red stripes and scientists are baffled as to why. The largest planet in our solar system is usually dominated by two dark bands in its atmosphere, with one in the northern hemisphere and one in the southern hemisphere.
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However, the most recent images taken by amateur astronomers have revealed the lower stripe known as the Southern Equatorial Belt has disappeared leaving the southern half of the planet looking unusually bare.
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The band was present in at the end of last year before Jupiter ducked behind the Sun on its orbit. However, when it emerged three months later the belt had disappeared.
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Journalist and amateur astronomer Bob King, also known as Astro_Bob, was one of the first to note the strange phenomenon.
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He said: "Jupiter with only one belt is almost like seeing Saturn when its rings are edge-on and invisible for a time - it just doesn't look right."
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It is not the first time this unusual phenomenon has been noticed. Jupiter loses or regains one of its belts every ten of 15 years, although exactly why this happens is a mystery.
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The planet is a giant ball of gas and liquid around 500 million miles from the Sun. It's surface is composed of dense red, brown, yellow, and white clouds arranged in light-coloured areas called zones and darker regions called belts.
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These clouds are created by chemicals that have formed at different heights. The highest white clouds in the zones are made of crystals of frozen ammonia. Darker, lower clouds are created from chemicals including sulphur and phosphorus. The clouds are blown into bands by
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Noted Jupiter watcher Anthony Wesley, who spotted an impact spot on its surface last year, has tracked the disappearing belt from his back garden in
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"It was obvious last year that it was fading. It was closely observed by anyone watching Jupiter," he told The Planetary Society.
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"There was a big rush on to find out what had changed once it came back into view."
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Mr Wesley said while it was a mystery as to what had caused the belt to fade, the most likely explanation was that it was linked to storm activity that preceded the change.
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"The question now is when will the South Equatorial belt erupt back into activity and reappear?" Mr Wesley said.
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The pattern for this happening is when a brilliant white spot forms in the southern zone. Gradually it will start to spout dark blobs of material which will be stretched by Jupiter's fierce winds into a new belt, and the planet will return to its familiar "tyre track" appearance.
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Jupiter will be closest to Earth on September 24, offering stargazers their best chance of seeing it without its stripe.
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