Astronomy Picture of the Day——不规则星系NGC 55

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Irregular Galaxy NGC 55

Image Credit & Copyright: Martin Pugh

Explanation:Irregular galaxy NGC 55 is thought to be similar to the Large Magellanic Cloud(LMC). But while the LMC is about 180,000 light-years away and is a well knownsatellite of our own Milky Way Galaxy, NGC 55 is more like 6 millionlight-years distant and is a member of the Sculptor Galaxy Group. Classified asan irregular galaxy, in deep exposures the LMC itself resembles a barred diskgalaxy. Spanning about 50,000 light-years, NGC 55 is seen nearly edge-onthough, presenting a flattened, narrow profile in contrast with our face-onview of the LMC. Just as large star forming regions create emission nebulae inthe LMC, NGC 55 is also seen to be producing new stars. This highly detailedgalaxy portrait highlights a bright core crossed with dust clouds, telltalepinkish star forming regions, and young blue star clusters in NGC 55.

不规则星系NGC 55

解释：这个不规则的星系NGC 55和大麦哲伦星系LMC十分相像，大麦哲伦星系距离我们约18万光年，是银河系最为人知的卫星星系，NGC55比LMC还要遥远，距我们约600万光年，是玉夫星系群的成员。

NGC55的覆盖范围有大约5万光年，侧对着我们地球，因此呈现出扁平而狭窄的样貌，这和正面地球的LMC形成了鲜明的对比。与LMC中的恒星形成区类似，NGC55也正在诞生很多新恒星。

这幅细节丰富的星系肖像突出了明亮的星系核，点缀着众多尘埃云，粉红色的恒星形成区以及年轻的蓝色星团。