M81
影像来源与版权:Paolo De Salvatore (Zenit Observatory)

说明:庞大而美丽的旋涡星系M81是地球天空中最明亮的星系之一,其大小与我们的银河系相近。这个亦称为NGC 3031或波德星系(波德是其18世纪的发现者)的宏伟旋涡位于北天的大熊星座方向。这幅精细的望远镜影像呈现了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。一些尘埃带实际上穿过了位于影像中央左侧的星系盘,与其他显著的旋涡特征形成了鲜明对比。这些不规则的尘埃带可能是M81与其较小的伴星系M82之间发生近距离交会的产物。通过对M81内变星的详细观测,我们完成了河外星系的最佳定距工作之一,这个距离为1180万光年。
翻译:北京天文馆

Messier 81
Image Credit & Copyright: Paolo De Salvatore (Zenit Observatory)

Explanation: One of the brightest galaxies in 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 reveals M81’s bright yellow nucleus, blue spiral arms, pink starforming regions, and sweeping cosmic dust lanes. Some dust lanes actually run through the galactic disk (left of center), contrary to other prominent spiral features though. The errant dust lanes may be the lingering result of a close encounter between M81 and its smaller companion galaxy, M82. Scrutiny of variable stars in M81 has yielded one of the best determined distances for an external galaxy — 11.8 million light-years.
Astronomy Picture of the Day 04/17/2019