哈勃太空望远镜拍摄到了一次巨型合并

This Hubble Picture of the Week features Arp 122, a peculiar galaxy that in fact comprises two galaxies — NGC 6040, the tilted, warped spiral galaxy and LEDA 59642, the round, face-on spiral — that are in the midst of a collision. This dramatic cosmic encounter is located at the very safe distance of roughly 570 million light-years from Earth.
ESA/Hubble & NASA, J. Dalcanton, Dark Energy Survey/DOE/FNAL/DECam/CTIO/NOIRLab/NSF/AURA Acknowledgement: L. Shatz

This NASA/ESA Hubble Space Telescope image features Arp 122, a peculiar galaxy that in fact comprises two galaxies – NGC 6040, the tilted, warped spiral galaxy and LEDA 59642, the round, face-on spiral – that are in the midst of a collision. This dramatic cosmic encounter is located at the very safe distance of roughly 570 million light-years from Earth. Peeking in at the lower-left corner is the elliptical galaxy NGC 6041, a central member of the galaxy cluster that Arp 122 resides in, but otherwise not participating in this monster merger.

Galactic collisions and mergers are monumentally energetic and dramatic events, but they take place on a very slow timescale. For example, the Milky Way is on track to collide with its nearest galactic neighbor, the Andromeda Galaxy (M31), but these two galaxies have a good four billion years to go before they actually meet. The process of colliding and merging will not be a quick one either: it might take hundreds of millions of years to unfold. These collisions take so long because of the truly massive distances involved.

Galaxies are composed of stars and their solar systems, dust, gas, and invisible dark matter. In galactic collisions, therefore, these constituent components may experience enormous changes in the gravitational forces acting on them. In time, this completely changes the structure of the two (or more) colliding galaxies, and sometimes ultimately results in a single, merged galaxy. That may well be what results from the collision pictured in this image. Galaxies that result from mergers are thought to have a regular or elliptical structure, as the merging process disrupts more complex structures (such as those observed in spiral galaxies). It would be fascinating to know what Arp 122 will look like once this collision is complete… but that will not happen for a long, long time.

Text credit: European Space Agency

这张哈勃太空望远镜拍摄本周图片展示了Arp 122，这是一个奇特的星系，实际上它包括两个处于碰撞中的星系——NGC 6040，一个倾斜扭曲的螺旋星系和LEDA 59642，一个圆形的螺旋面星系。这场戏剧性的宇宙邂逅位于距离地球约5.7亿光年的非常安全的距离处。
影像来源: ESA/Hubble & NASA, J. Dalcanton, Dark Energy Survey/DOE/FNAL/DECam/CTIO/NOIRLab/NSF/AURA Acknowledgement: L. Shatz

这张NASA/ESA哈勃太空望远镜拍摄的图像显示了Arp 122，这是一个特殊的星系，实际上它包括两个处于碰撞中的星系——NGC 6040，一个倾斜扭曲的螺旋星系和LEDA 59642，一个圆形的螺旋面星系——这两个星系正在碰撞中。这场戏剧性的宇宙邂逅位于距离地球约5.7亿光年的非常安全的距离处。左下角是椭圆星系NGC 6041，它是Arp 122所在星系团的核心成员，但除此之外没有参与这次巨大的合并。

星系碰撞和合并是极其剧烈的事件，但它们发生的时间非常缓慢。例如，银河系正在与它最近的星系邻居仙女座星系（M31）相撞，但这两个星系在真正相遇之前还有整整40亿年的时间。碰撞和合并的过程也不会是一个快速的过程：它可能需要数亿年才能展开。这些碰撞之所以持续如此之久，是因为它们之间的距离实在太遥远了。

星系由恒星及其太阳系、尘埃、气体和看不见的暗物质组成。因此，在星系碰撞中，这些组成部分可能会经历作用在它们身上的引力的巨大变化。随着时间的推移，这完全改变了两个（或更多）碰撞星系的结构，有时最终会形成一个合并的星系。这很可能就是这张照片上的碰撞所产生的结果。由于合并产生的星系被认为具有规则或椭圆形结构，因为合并过程会破坏更复杂的结构（例如在螺旋星系中观察到的结构）。一旦这次碰撞完成，知道Arp 122会是什么样子会很有趣……但这在很长很长一段时间内都不会发生。

文稿来源: European Space Agency