These images taken by NASA's Hubble Space Telescope show four members of the Virgo cluster of galaxies, the nearest large galaxy cluster to Earth. They are part of a survey of globular star clusters in 100 of Virgo's galaxies. The Hubble study found evidence that these globulars are more likely to form in dense areas, where star birth occurs at a rapid rate, instead of uniformly from galaxy to galaxy.
NASA/ESA/E. Peng (Peking University, Beijing)