Stephan’s Quintet
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In 1877, astronomer Edouard Stephan made a startling discovery in the constellation Pegasus: five galaxies in close proximity to one another! As it turns out, he was mistaken, but the mistake was not recognized until very recently, when it became possible to accurately determine how many millions of light years separate us from distant galaxies. The galaxy at the lower left in this photo, known as NGC1320, is 40 million light-years away, while the other four galaxies are 290 million light-years away.
But those other four galaxies are very close together! In fact, they are so close that the energy generated by their proximity is unequalled by any other than has so far been discovered in the entire universe! The two galaxies at center (NGC7318A and NGC 7318B, see detail below) are about to merge into one, and their gravitational interaction has generated a shockwave, or perhaps a cloud consisting of millions of shockwaves, extending over a distance greater than the size of our Milky Way.
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