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At a mere 45-65 million light years of distance, the Antennae Galaxies are the nearest, and perhaps the youngest examples of a pair of colliding galaxies. Their interaction began less than a billion years ago, as they drew towards one another, and then over the next 300 million years, came together and passed through one another. Astronomers believe that gravitational forces will eventually stop them from parting completely, and then, inexorably, they will collapse together into a single huge galaxy.
The collision released vast amounts of energy, creating billions of new stars, which can be discerned in the photo as the bright blue and pink areas. The bright white regions are the nuclei of the two galaxies. Not seen in this photo are the trails of stellar gases and dust that extend in opposite arcs away from the galaxies, the result of gravitational forces known as “galactic tides”.