双鱼座的壳状星系

2020年8月27日

Shell Galaxies in Pisces
Image Credit & Copyright: Martin Pugh

Explanation: This intergalactic skyscape features a peculiar system of galaxies cataloged as Arp 227 some 100 million light-years distant. Swimming within the boundaries of the constellation Pisces, Arp 227 consists of the two galaxies prominent right of center, the curious shell galaxy NGC 474 and its blue, spiral-armed neighbor NGC 470. The faint, wide arcs or shells of NGC 474 could have been formed by a gravitational encounter with neighbor NGC 470. Alternately the shells could be caused by a merger with a smaller galaxy producing an effect analogous to ripples across the surface of a pond. The large galaxy on the top lefthand side of the deep image, NGC 467, appears to be surrounded by faint shells too, evidence of another interacting galaxy system. Intriguing background galaxies are scattered around the field that also includes spiky foreground stars. Of course, those stars lie well within our own Milky Way Galaxy. The field of view spans 25 arc minutes or about 1/2 degree on the sky.

Tomorrow’s picture: in the valley

双鱼座的壳状星系
影像提供与版权: Martin Pugh

说明: 这张星系际影像，呈现离我们约1亿光年远，编录号为Arp 227的奇特天体系统。位在双鱼座内的Arp 227，成员是影像中右方的二个醒目星系 ，包括有趣的壳状星系NGC 474和它的泛蓝螺旋状伴星系NGC 470。星系NGC 474黯淡宽广弧状或壳层构造，可能是和邻近NGC 470发生重力接近所致。另一种可能的起源则是：它和另一个小星系合并，因此产生很像水塘表面涟漪的效应。在这张深空影像上左方的大星系NGC 467，周围看似也环拱有壳状结构，而这也指证它也是一个重力互扰星系。在这片星野中，除了很有趣的背景星系之外，也有带着星芒近在我们银河系内的前景恒星。这幅影像跨幅为25角分，或者说是接近半度的天空。

明日的图片: in the valley