galactic arm

例句：

1. 1. The discovery of the galaxy's central black hole has changed our understanding of the cosmos.
   发现星系中心的黑洞改变了我们对宇宙的理解。
2. 2.The galactic arm is a region of space where stars are found in close proximity to each other.
   银河臂是一片空间区域，其中恒星彼此相距很近。
3. 3.The study of galactic arms can provide valuable insights into the formation and evolution of galaxies.
   研究银河臂可以为了解星系的形成和演化提供宝贵的见解。