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Whirlpool GalaxyThis penetrating look at the Whirlpool Galaxy won Australia's Martin Pugh top prize in the 2012 Astronomy Photographer of the Year competition. The contest, run by the U.K.'s Royal Observatory Greenwich, drew nearly 850 entries this year from around the world.Here, a spiral arm of the Whirlpool Galaxy grazes the light of a smaller companion galaxy that's slowly being torn apart by its neighbor's gravity.The galaxies—some 20 million light-years away—are too faint and distant for the human eye to register their hues. But this long photographic exposure allows us to appreciate their colorful nature, said Marek Kukula, the Royal Observatory's public astronomer and a contest judge. Young stars appear blue, he explained, and hydrogen gas in the spiral arms varies from pink to reddish.Pugh's picture impressed judges with its depth, clarity, and color."It's not just the detail in the spiral arms that's remarkable," said judge Will Gater. "Look closely and you'll see many, very distant galaxies in the background too."The winning pictures in the competition's four categories are on view at the Royal Observatory through February 2013.(Also see "Pictures: Best Amateur Astronomy Images Announced [2011].")—Luna Shyr

Photograph courtesy Martin Pugh, APOY/Royal Observatory