Astronomy Picture of the Day——梅西耶第五天体
Messier 5
Image Credit & Copyright: Adam Block,Mt. Lemmon Sky Center
Explanation: "Beautiful Nebuladiscovered between the Balance [Libra] & the Serpent [Serpens] ..."begins the description of the 5th entry in 18th century astronomer CharlesMessier's famous catalog of nebulae and star clusters. Though it appeared toMessier to be fuzzy and round and without stars, Messier 5 (M5) is now known tobe a globular star cluster, 100,000 stars or more, bound by gravity and packedinto a region around 165 light-years in diameter. It lies some 25,000light-years away. Roaming the halo of our galaxy, globular star clusters areancient members of the Milky Way. M5 is one of the oldest globulars, its starsestimated to be nearly 13 billion years old. The beautiful star cluster is apopular target for earthbound telescopes. Even close to its dense core, thecluster's red and blue giant stars, and rejuvenated blue stragglers stand out with yellowish and blue hues in this sharp color image.
梅西耶第五天体
“它是天秤座和巨蛇座之间的美丽星云……”，这是18世纪天文学家查尔斯·梅西耶对其著名的星云和星团目录中第5个天体的描述。虽然被梅西耶认为是一个没有恒星的浑圆、模糊的天体，但是，在我们现在的认知中，M5是一个由10万颗甚至更多恒星构成的球状星团，这些恒星在引力作用下聚集在一片直径约165光年的区域内。M5距离地球约25000光年。漫游在银河系光晕中的球状星团是银河系中的古老成员。M5是最古老的球状星团之一，它内部的恒星年龄估计可达130亿年。这个美丽的星团是地面望远镜观测的最热目标之一。在这幅高清彩色照片中，靠近M5致密核心的红巨星和蓝巨星，以及活跃的蓝离散星分别呈现出淡黄色和蓝色光泽。
参考文献：
https://apod.nasa.gov/apod/image/1905/m5sBlock.jpg
近期文章：
Astronomy Picture of the Day——朱诺号拍摄到”大理石”