Astronomy Picture of the Day——螺旋星系M81
Messier 81
Image Credit & Copyright: Paolo DeSalvatore (Zenit Observatory)
Explanation: One of the brightest galaxiesin planet Earth's sky is similar in size to our Milky Way Galaxy: big,beautiful Messier 81. Also known as NGC 3031 or Bode's galaxy for its 18th century discoverer, this grand spiral can be found toward the northern constellation of Ursa Major, the Great Bear. The detailed telescopic view revealsM81's bright yellow nucleus, blue spiral arms, pink starforming regions, andsweeping cosmic dust lanes. Some dust lanes actually run through the galacticdisk (left of center), contrary to other prominent spiral features though. Theerrant dust lanes may be the lingering result of a close encounter between M81and its smaller companion galaxy, M82. Scrutiny of variable stars in M81 hasyielded one of the best determined distances for an external galaxy 11.8million light-years.
M81
庞大而又美丽的旋涡星系M81是天空中最明亮的星系之一，其大小与我们的银河系相仿。M81也被称为NGC 3031或波德星系（波德是发现者），位于北天的大熊星座方向。这幅精细的图片呈现了M81亮黄色的星系核，蓝色的旋臂，粉红色的恒星形成区以及广阔的宇宙尘埃带。尘埃带穿过了位于影像中央左侧的星系盘，与其显著的旋涡特征形成了鲜明的对比。这些不规则的尘埃带有可能是M81与其相对较小的伴星系M82发生近距离交会时的产物。通过对M81内变星的详细观测，我们完成了银河外星系的最佳定距工作之一，它距离地球1180万光年。
参考文献：
https://apod.nasa.gov/apod/image/1904/M81salvatore.jpg
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Astronomy Picture of the Day——锥状星云的附近