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Of all the galaxies that adorn the cosmos, the most majestic are the stunning spirals such as our home galaxy, the Milky Way. But astronomers have long thought that the most luminous galaxies in the universe are a less attractive type known as ellipticals, which look like fuzzy footballs. Recently, though, a search turned up a new breed of spiral: mammoth galaxies whose size and brightness rival the greatest ellipticals in the universe.
These “super-spiral” galaxies are extremely rare. In fact, the closest example is more than a billion light-years from Earth. The search identifed 53 of them. Each emits eight to 14 times more visible light than the Milky Way, which itself is brighter than most other galaxies. And the largest of them, in the constellation Hercules, has a disk of stars that’s four times larger than the Milky Way’s.
Now that astronomers have discovered these spectacular galaxies, they’re struggling to understand how they formed. Galaxies grow bigger when they gobble up other galaxies. But such violence can disrupt a galaxy’s delicate spiral arms and transform it into an elliptical. Indeed, that may explain why most of the largest galaxies in the universe are ellipticals rather than spirals. Yet somehow the super spirals managed to do what seemed to be impossible: They grew to enormous proportions while retaining their exquisite beauty.
Tomorrow: Taking a thousand pictures all at once.
Script by Ken Croswell, Copyright 2015