Astronomy Picture of the Day——梅西耶2星云
Messier 2
Image Credit: ESA/Hubble & NASA, G.Piotto et al.
Explanation: After the Crab Nebula, M1,this giant star cluster is the second entry in 18th century astronomer CharlesMessier's famous list of things that are not comets. M2 is one of the largestglobular star clusters now known to roam the halo of our Milky Way galaxy.Though Messier originally described it as a nebula without stars, this stunningHubble image resolves stars across the central 40 light-years of M2. Itspopulation of stars numbers close to 150,000, concentrated within a totaldiameter of around 175 light-years. About 55,000 light-years distant toward theconstellation Aquarius, this ancient denizen of the Milky Way, also known asNGC 7089, is 13 billion years old.
梅西耶2星云
继蟹状星云M1之后，M2是18世纪天文学家查尔斯.梅西耶编录的著名非彗星星表中的第二个天体。M2是目前已知的，漫游在银河系上的最大球状星团之一。虽然最初梅西耶将它描述为一个没有恒星的星云，但是这幅由哈勃拍摄的绝美照片中可以发现M2中央40光年区域内的恒星。其内恒星数量接近15万颗，集中在直径约175光年的区域内。这个古老的银河系居民位于水瓶座方向，距离地球约55,000光年，它也被称为NGC7089，年龄超过130亿年。
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Astronomy Picture of the Day——马头星云四周的云气丝