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這是木星探測器伽利略號拍得小行星951的照片，也是第一幀從近距離拍得的小行星照。在火星和木星軌道之間運行著無數的小行星，第一顆小行星是在1801年1月1日被皮亞齊所發現，其實皮亞齊當時正在搜尋另一顆恆星，他並沒有發現該恆星，卻意外地看到一顆移動的天體。數月後，當他的發現最終被公開時，這顆星體已運行到太陽的背後。為了證實皮亞齊的發現，24歲的高斯（著名數學家）發揮了他的天份，精確運算出該星體從太陽背後重現時的方位。當天文學家再次尋獲這顆星體時，剛好是1801年的最後一天！皮亞齊把他的星體命名為穀神星，最初，穀神星被普遍認受為一顆行星，次年，英國天文學家威廉．赫歇爾把它降格為小行星，國際天文聯會在2006年又把它編入矮行星行列。
The story of the first asteroid
This is Gaspra. It is the first asteroid photo taken at close range. The very first asteroid was discovered on 1 January 1801, by Giuseppe Piazzi. Piazzi was looking for a star when he spotted a moving star-like object. His finding was made public in September that year. By that time the object was too close to the sun's glare for observation. To enable astronomers to confirm the existence of Piazzi's star, 24-year-old Carl Friedrich Gauss (German mathematician) made some calculations. On the last day of 1801, the object was recovered near its predicted position. The moving star was named Ceres by its original discoverer and was thought to be a planet until Sir William Herschel coined it as an asteroid in 1802. In 2006, the International Astronomical Union catalogued Ceres as a ‘dwarf planet’. ■甄枝強 資深天文愛好者Image Courtesy USGS/NASA/JPL
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