Merging star clusters seen by Hubble

US astronomers using NASA's Hubble Space Telescope say they've have caught two clusters of massive stars that may be in the early stages of merging. What was first thought to be one cluster in the core of the massive star-forming region 30 Doradus, also known as the Tarantula Nebula, has been found to be a composite of two clusters that differ in age by about 1 million years, a NASA release reported Thursday. The clusters are 170,000 light-years away in the Large Magellanic Cloud, a small satellite galaxy to our Milky Way. Smaller systems that merge into larger ones could help to explain the origin of some of the largest known star clusters, astronomers said. Elena Sabbi of the Space Telescope Science Institute in Baltimore, Md., and her colleagues first began looking at the area while searching for runaway stars, fast-moving stars that have been kicked out of their stellar nurseries where they first formed. Some astronomers say they believe the giant gas clouds out of which star clusters form may fragment into smaller pieces, and once these small cluster precipitate stars, they might then interact and merge to become a bigger system. This interaction is what Sabbi and her team say they think they are observing in 30 Doradus.