M5
影像来源与版权:Adam Block, Mt. Lemmon SkyCenter, University of Arizona

说明:“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·梅西耶对其著名星云和星团目录中第5个天体的描述。虽然,梅西耶认为M5是一个浑圆、模糊的天体,而且没有恒星,但是,我们现在知道它是一个由10万颗或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距离我们约2万5千光年远。漫游在我们银河系光晕中的球状星团是银河系的古老成员。M5是最古老的球状星团之一,它的恒星年龄估计将近有130亿年。这个美丽的星团是地面望远镜观测的一个热门目标。在这幅高清彩色影像中,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色泽。
翻译:北京天文馆

Messier 5
Image Credit & Copyright: Adam Block, Mt. Lemmon SkyCenter, University of Arizona

Explanation: “Beautiful Nebula discovered between the Balance [Libra] & the Serpent [Serpens] …” begins the description of the 5th entry in 18th century astronomer Charles Messier’s famous catalog of nebulae and star clusters. Though it appeared to Messier to be fuzzy and round and without stars, Messier 5 (M5) is now known to be a globular star cluster, 100,000 stars or more, bound by gravity and packed into a region around 165 light-years in diameter. It lies some 25,000 light-years away. Roaming the halo of our galaxy, globular star clusters are ancient members of the Milky Way. M5 is one of the oldest globulars, its stars estimated to be nearly 13 billion years old. The beautiful star cluster is a popular target for earthbound telescopes. Even close to its dense core, the cluster’s red and blue giant stars, and rejuvenated blue stragglers stand out with yellowish and blue hues in this sharp color image.
Astronomy Picture of the Day 05/09/2019