Astronomy Picture of the Day——M95：带内环的旋涡星系
M95: Spiral Galaxy with an Inner Ring
Image Credit: NASA, ESA, Hubble, ESO,Amateur Data; Processing & Copyright: Robert Gendler & RobertoColombari
Explanation: Why do some spiral galaxieshave a ring around the center? First and foremost, M95 is one of the closerexamples of a big and beautiful barred spiral galaxy. Visible in the featured combination of images from Hubble and several ground based telescopes aresprawling spiral arms delineated by open clusters of bright blue stars, lanesof dark dust, the diffuse glow of billions of faint stars, and a short baracross the galaxy center. What intrigues many astronomers, however, is the circum nuclear ring around the galaxy center visible just outside the centralbar. Although the long term stability of this ring remains a topic of research, observations indicate its present brightness is at least enhanced by transient bursts of star formation. M95, also known as NGC 3351, spans about 50,000 light-years, lies about 30 million light years away, and can be seen with asmall telescope toward the constellation of the Lion (Leo).
M95：带内环的旋涡星系
为什么有些旋涡星系的中央会有一个光环？首先，M95是一个庞大且美丽的棒旋状星系，而且距离地球相对比较近。在这幅由哈勃和数台地面望远镜拍摄的多张照片拼接合成的特征影像中，可以看到由亮蓝色疏散星团勾勒出的蜿蜒旋臂、黑暗色尘埃带、数十亿颗黯淡恒星弥散的辉光以及横跨星系中央的短棒状结构。然而，令许多天文学家感兴趣的是中央短棒外、围绕星系中央核心的光环。虽然这个光环的长期稳定性仍然是一个值得研究的课题，但观测结果表明，它目前的亮度因恒星形成的短暂爆发而有些许增强。M95亦称为NGC 3351，大小约为5万光年，距离地球约3千万光年，在地面上朝着狮子座方向，用小型望远镜就可以观测到它。
参考文献：
https://apod.nasa.gov/apod/image/1905/M95_HstEsoGendler_1800.jpg
近期文章：
Astronomy Picture of the Day——NGC 3572附近的恒星、尘埃和气体