Hubble image captures puzzling star group GREENBELT, Md., Feb. 9 (UPI) -- U.S. astronomers say a distant galaxy puzzles them because it contains a high number of stars younger than their neighbors, which goes against current theory. The deep space object, captured in a Hubble space telescope image, is called NGC 6752 and is a globular cluster more than 10 billion years old. That makes it one of the oldest collections of stars knows, blazing for more than twice as long as our solar system has existed, a NASA release said. What puzzles scientists is NGC 6752 contains a high number of so-called "blue straggler" stars, some of which are visible in the Hubble image, that display characteristics of stars younger than their neighbors despite models suggesting most stars within globular clusters should have formed at about the same time. One possible reason, astronomers said, is that a very large number of the stars -- up to 38 percent -- in the cluster's core are in binary systems. Collisions between stars in this turbulent area could produce the blue stragglers that are so prevalent, they said.