水瓶座两个星系正在发生碰撞

Peace is the curious name given to a pair of interacting and merging¹ galaxies² that lie around 220 million light-years away in the constellation³（星座，荟萃） of Aquarius. It is also known as NGC 7252 and Arp 226 and is just bright enough to be seen by amateur（业余的，外行的） astronomers⁴ as a very faint small fuzzy blob. This very deep image was produced by ESO's Wide Field Imager on the MPG/ESO 2.2-metre telescope at ESO's La Silla Observatory⁵ in Chile. A galaxy⁶ collision is one of the most important processes influencing how our Universe evolves, and studying them reveals important clues about galactic ancestry⁷. Luckily, such collisions are long drawn-out events that last hundreds of millions of years, giving astronomers plenty of time to observe them.

This picture of Atoms-for-Peace represents a snapshot of its collision, with the chaos⁸ in full flow, set against a rich backdrop of distant galaxies. The results of the intricate（复杂的，错综的） interplay of gravitational interactions can be seen in the shapes of the tails made from streams of stars, gas and dust. The image also shows the incredible shells that formed as gas and stars were ripped out of the colliding galaxies and wrapped around their joint⁹ core. While much material was ejected into space, other regions were compressed, sparking bursts of star formation. The result was the formation of hundreds of very young star clusters, around 50 to 500 million years old, which are speculated to be the progenitors¹⁰（先祖，先觉者） of globular clusters（球状星团） .

Atoms-for-Peace may be a harbinger（先驱，前兆） of our own galaxy's fate. Astronomers predict that in three or four billion years the Milky¹¹ Way and the Andromeda Galaxy will collide, much as has happened with Atoms-for-Peace. But don't panic: the distance between stars within a galaxy is vast, so it is unlikely that our Sun will end up in a head-on collision with another star during the merger¹².

The object's curious nickname has an interesting history. In December 1953, President Eisenhower gave a speech that was dubbed¹³（被称为） Atoms for Peace. The theme was promoting nuclear power for peaceful purposes — a particularly hot topic at the time. This speech and the associated conference made waves in the scientific community and beyond to such an extent that NGC 7252 was named the Atoms-for-Peace galaxy. In many ways, this is oddly appropriate: the curious shape that we can see is the result of two galaxies merging to produce something new and grand, a little like what occurs in nuclear fusion¹⁴. Furthermore, the giant loops resemble a textbook diagram of electrons orbiting an atomic nucleus¹⁵.