持續擴張的霍姆斯彗星
Expansive Comet Holmes
霍姆斯彗星球狀的彗髮已經膨脹到超過一百四十萬公里了，稀薄的雲氣甚至已經比太陽還大。這個反射陽光，充滿塵埃和氣體的彗髮，是由活躍的彗核噴發而出，而在 10 月的爆發之前大小僅有 3.4 公里。這張銳利的影像，是由加拿大-法國-夏威夷望遠鏡 (CFHT)於 11 月 14 日所拍攝，透過外圍的彗髮仍可看到後方的星星，而彗核則深埋在中間最緻密且明亮的區域之中。彗髮最明亮的區域已經稍微偏離中心了，這是因為有一塊大型碎片飄離彗核，並且碎裂，導致這次的大爆發。當然，由於霍姆斯彗星正橫越英仙座，最近的影像可看到彗星旁有著一顆明亮的天船三 (英仙座 α 星)。
The spherical coma of Comet Holmes has swollen to a diameter of over 1.4 million kilometers, making the tenuous, dusty cloud even bigger than the Sun. Scattering sunlight, all that dust and gas came from the comet’s remarkably active nucleus, whose diameter before the late October outburst was estimated to be a mere 3.4 kilometers. In this sharp image, recorded on November 14 with the Canada-France-Hawaii Telescope, stars are easily visible right through the outer coma, while the nucleus is buried inside the condensed, bright region. The bright region of the coma seems offset from the center, consistent with the idea that a large fragment drifted away from the nucleus and disintegrated, producing the comet’s spectacular outburst. Of course, more recent images of Holmes also show the bright star Mirfak (Alpha Persei) shining through as the comet sweeps slowly through the constellation Perseus.
Posted in Astronomy Picture of the Day, Comet, 彗星, 每日一天文圖
