哈勃望远镜拍摄的斯蒂芬五重星系
影像来源与版权:NASA, ESA, Hubble; Processing: Daniel Nobre

说明:这些庞大星系是什么时候开始跳舞的?实际上,斯蒂芬五重星系中只有四个星系被禁锢在距离我们约3亿光年远处发生的一次密近交会的宇宙探戈中。在这幅由哈勃太空望远镜拍摄、最近经过再加工的影像中,我们很容易发现这个由多个相互作用星系构成的奇特星系,它们都呈现出淡黄色色泽,从左到右分别是NGC 7319、7318B、7318A和7317。它们也有扭曲的环状和尾部结构,在破坏性引力潮的影响下演变。影像左下方的庞大星系NGC 7320位于距离我们约4千万光年远的前景中,因此它并不是相互作用星系群的一部分。数据和建模表明NGC 7318B是一个相对较新的入侵者。最近在斯蒂芬五重星系附近发现由古老红星组成的光晕表明至少有一些星系已经纠缠在一起超过了十亿年。我们使用一台中等大小的望远镜朝向飞马座方向便能看到斯蒂芬五重星系。
翻译:北京天文馆

Stephan’s Quintet from Hubble
Image Credit & Copyright: NASA, ESA, Hubble; Processing: Daniel Nobre

Explanation: When did these big galaxies first begin to dance? Really only four of the five of Stephan’s Quintet are locked in a cosmic tango of repeated close encounters taking place some 300 million light-years away. The odd galaxy out is easy to spot in this recently reprocessed image by the Hubble Space Telescope — the interacting galaxies, NGC 7319, 7318B, 7318A, and 7317 (left to right), have a more dominant yellowish cast. They also tend to have distorted loops and tails, grown under the influence of disruptive gravitational tides. The mostly bluish galaxy, large NGC 7320 on the lower left, is in the foreground at about 40 million light-years distant, and so is not part of the interacting group. Data and modeling indicate that NGC 7318B is a relatively new intruder. A recently-discovered halo of old red stars surrounding Stephan’s Quintet indicate that at least some of these galaxies started tangling over a billion years. Stephan’s Quintet is visible with a moderate sized-telescope toward the constellation of Winged Horse (Pegasus).
Astronomy Picture of the Day 06/03/2019