Blue Straggler Stars in Globular Cluster M53
Image Credit: ESA/Hubble, NASA
Explanation: If our Sun were part of this star cluster, the night sky would glow like a jewel box of bright stars. This cluster, known as M53 and cataloged as NGC 5024, is one of about 250 globular clusters that survive in our Galaxy. Most of the stars in M53 are older and redder than our Sun, but some enigmatic stars appear to be bluer and younger. These young stars might contradict the hypothesis that all the stars in M53 formed at nearly the same time. These unusual stars are known as blue stragglers and are unusually common in M53. After much debate, blue stragglers are now thought to be stars rejuvenated by fresh matter falling in from a binary star companion. By analyzing pictures of globular clusters like the featured image taken by the Hubble Space Telescope, astronomers use the abundance of stars like blue stragglers to help determine the age of the globular cluster and hence a limit on the age of the universe. M53, visible with a binoculars towards the constellation of Bernice’s Hair (Coma Berenices), contains over 250,000 stars and is one of the furthest globulars from the center of our Galaxy.
Tomorrow’s picture: ripple stars
影像提供: ESA/Hubble, NASA
说明: 如果太阳是这个星团的成员，那么地球的夜空将会是由亮星缀而成的珠宝盒。这个名为M53（NGC 5024）的星团，是本银河系内孑存的250个球状星团之一。 M53大多数的恒星都比太阳还老，颜色也比太阳红，但是少数谜样的恒星之色泽却偏蓝，而且较年轻。这些年轻的恒星，似乎与M53内的恒星皆几乎同时诞生之假说牴触。此外，在M53里头，这些称为蓝掉队星的不寻常恒星蛮常见的。经过反覆推敲，现在认为蓝掉队星是双星系统的成员，是老年恒星接收来自伴星的新物质，所发生的回春现象。经由分析像这幅哈伯太空望远镜主题影像里的球状星团，天文学家可用蓝掉队星的数量，定出球状星团的年龄，进而找出宇宙年龄的上限。位在后发座方向、拥有250万颗成员星的M53，是双筒望远镜可见的天体，同时也是离银河系中心最遥远的球状星团之一。 （掉队星=离散星）
明日的图片: ripple stars