A paper released in Science last week detailed research that showed globular clusters may be more noncommittal than previously thought. The spherical collections of stars are normally anchored to a single galaxy, but a new study shows that there may be some globular clusters that are currently between galaxies, floating within galaxy clusters and looking for a new home. Scientists are hoping that by tracking globular clusters as they settle down in a new galaxy, the motion could provide information about the effects of dark matter.Globular clusters usually sit in the halo, or in the vicinity of the disk, of a single galaxy. However, since we've been finding other objects—like red giants and planetary nebulae—in the no-man's land between galaxies, scientists thought they might find globular clusters that are also under the gravitational influence of multiple galaxies at once.
A survey of the sky turned up a few rogue globular clusters in the galaxy cluster Virgo, 54 million light years away, hanging around in the space among galaxies M87, M49, and M60. Most of the globular clusters emitted light that was bluish in color, indicating they did not contain much metal (metal-rich globular clusters are reddish, and the subject of some recent news). Their lack of metal content suggests that they are recently divorced from smaller dwarf galaxies.
Scientists will watch the globular clusters closely as they move under the galaxies' gravitational influence, looking for indications that they're likely to settle down with a single galaxy. Since scientists generally know the masses of these objects, studying their trajectories and controlling for gravitational behavior caused solely by each object's mass could provide new measurements on the effects of dark matter.
Science, 2010. DOI: 10.1126/science.1186496
Source: Arstechnica.com
