 放大圖片
1994年7月，天文界發生了一件大事──21塊彗星碎片隕落木星表面。此次事件為天文學家就行星表面環狀坑穴的形成提供了實證，也導致行星際隕擊造成恐龍滅絕的猜想忽然變成人類的現代「啟示錄」。次年國際天文聯盟的年會提出了「太空防衛計劃」的構思，各國紛紛對有機會飛近地球，並對地球產生威脅的天體進行搜索和監察。至今年5月的統計，已發現五千四百多顆所謂「近地天體」，慶幸這當中尚未有一顆被定格為對地球存在威脅。附圖為木星於彗星隕擊前（右）後（左）的比較，紅箭頭標示著名的「大紅斑」，白箭頭指示彗星碎片隕擊痕跡。
Inspiration from a cometary impact
In the summer of 1994, 21 pieces of cometary debris impacted the great planet Jupiter. It was the first time ever, in the history of the human race, that such an event was witnessed. It provided evidence of how impact craters were formed on the surfaces of the moon and other planets. All of a sudden, the hypothesis of an asteroidal impact resulting an extensive mass extinction some 65 million years ago becomes Apocalypse of the modern age. In the subsequent years, ‘Spaceguard organizations’ were formed in different countries in support of the search and study of near-Earth objects. So far, more than 5400 such objects have been identified. ■甄枝強 香港天文學會
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放大圖片
