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31. 星系吞食 Galactic cannibalism refers to the process by which a large galaxy, through tidal gravitational interactions with a companion, merges with that companion, resulting in a larger, often irregular galaxy. The most common result of the gravitational merger of two or more galaxies is an irregular galaxy of one form or another, although elliptical galaxies may also result. It has been suggested that galactic cannibalism is currently occurring between the Milky Way and the Large and Small Magellanic Clouds. Streams of gravitationally-attracted hydrogen arcing from these dwarf galaxies to the Milky Way is taken as evidence for this theory. A long time ago, in a galaxy far, far away, the real battle of star wars was wreaking havoc on two galaxies. These two galaxies, known as the Antennae Galaxies, were locked in a cosmic battle of tug-of-war. This process of galactic destruction is more common than once thought, and may even contribute to the growth of some galaxies. Figure 1: The Antennae Galaxies1 Each galaxy contains billions and billions of stars. This makes galaxies extraordinarily heavy, or massive, and massive objects can exert very strong gravitational forces in space. Just as Earth can feel the pull of the Sun from millions of miles away, so too can a galaxy feel the gravitational tug of another galaxy. This gravitational tug is much stronger for massive objects like galaxies than it is for our Sun, so galaxies that are millions of light-years away from each other can still feel the pull of another massive galaxy, even though they are so far apart. Like the Antennae Galaxies , two galaxies that feel the tug of each other will race towards each other at incredible speeds, eventually colliding in a galactic display of fireworks. | 
