charles 2009-3-27 10:47
Collinder 399: 掛衣架星群
Collinder 399: The Coat Hanger
[img]http://i7.tinypic.com/2wlr0g5.jpg[/img]
Credit & Copyright: Frank Barrett (Celestial Wonders)
[color=navy]Explanation: [/color]
[color=dimgray]Is this coat hanger a star cluster or an asterism? This cosmic hang-up has been debated over much of last century, as astronomers wondered whether this binocular-visible object is really a physically associated open cluster or a chance projection. Chance star projections are known as asterisms, an example of which is the popular Big Dipper. Recent precise measurements from different vantage points in the Earth's orbit around the Sun have recently uncovered discrepant angular shifts indicating that the Coat Hanger is better described as an asterism. Known more formally as Collinder 399, this bright stellar grouping can be seen spanning more than a full moon toward the direction of the constellation of the Fox (Vulpecula). On the far right of the above image is the open cluster of stars NGC 6802. [/color]
[color=navy]說明:[/color]
[color=dimgray](Collinder 399 是疏散星團圖鑑編號399的星體) 這個形狀像是掛衣架的星群是星團(star cluster)還是星座(asterism)呢? 這樣的宇宙謎題 在上個世紀被爭論很久，因為天文學家懷疑這個用雙眼望遠鏡就可見到的星群，實際上是疏散星團或只是投影的巧合呢? 投影的巧合在天文上的例子，就是北斗七星(Big Dipper)。 最近從地球繞太陽的軌道 不同的位置，進行較精準的測量，發現掛衣鉤的星體中有不同的角度上的移動，暗示著掛衣鉤的星體應該是星座，也就是投影的巧合。 這個被大家所熟知的 Collinder 399，亮星能夠橫跨大約是滿月的大小，在 狐狸座的方向， 影像中最右上角的是疏散星團 NGC 6802。 [/color]
[size=2]資料來源: Scientific American
Department of Physics, NCKU[/size][color=white][size=1]
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