NASA-International Space Station

Imagine discovering a living dinosaur in your backyard. Astronomers have found the astronomical corresponding of prehistoric life in our intergalactic backyard: a group of small, early galaxies that has waited 10 billion years to come together. These "late bloomers" are on their way to building a large elliptical galaxy.

Such encounters between dwarf galaxies are usually seen billions of light-years away and therefore occurred billions of years ago. But these galaxies, members of Hickson Compact Group 31, are comparatively nearby, only 166 million light-years away.

New images of this foursome by NASA's Hubble Space Telescope offer a window into the determining years of the universe, when the buildup of large galaxies from smaller construction blocks was common. The analysis was bolstered by infrared data from NASA's Spitzer Space Telescope and ultraviolet observations from NASA's Galaxy Evolution Explorer and Swift satellite. Those data helped the astronomers measure the total amount of star formation in the system.