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Cosmic Orphans: Stray Stars Found Wandering Between Galaxies
By Robert Roy Britt
Senior Science Writer
posted: 06:00 am ET
17 July 2003
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EMBARGOED FOR Clusters of old stars not large enough to be considered galaxies have been found wandering through otherwise sparse regions between galaxies. Most were probably kicked out of their former homes by violent galactic interactions, astronomers said. The gatherings, called globular clusters, are among the oldest structures in the universe. They contain mostly aged stars that date back to the first few billion years of the universe. As many as a million of these old stars are sometimes huddled into a dense pack that makes a globular cluster. Scientists think globular clusters are among the building blocks of galaxies. Our own Milky Way Galaxy is surrounded by about 150 globular clusters, all gravitationally bound to the larger host. Astronomers liken them to bees swarming around a hive. Untold others have been consumed and integrated into the galaxy through time. The newfound clusters, so dim the stretch the capabilities of the world's greatest telescopes, are about 400 million light-years from Earth. "These clusters are no longer held within the gravitational grip of galaxies, and seem to be wandering freely through intergalactic space like cosmic vagabonds," said Michael West, an astronomer at the University of Hawaii. West said the clusters probably once resided in galaxies and were booted into the cosmic hinterlands by the gravitational effects of colliding galaxies. Theory had long predicted as much. A preliminary report of the discoveries was made available to scientists in April. Images from the Hubble Space Telescope and the Keck Telescope in Hawaii were used to confirm the findings. West presented the results in Australia this week at a meeting of the International Astronomical Union. West and his colleagues figure studying the scenes will shed light on the numbers of types of galaxies that have been destroyed so far in the universe. Meanwhile, not all of the orphaned globular star clusters will necessarily remain so. "Some of these star clusters might also eventually be 'adopted' by other galaxies if they stray close enough to be captured by their gravity," West said.
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