The Pleiades-a nearby cluster easily visible in the western sky on a winter evening-is the site of an extraordinary three-way celestial collision, says astrophysicist Richard White, formerly of Smith College in Massachusetts. Sensitive telescopic images show the 500 or so stars of the Pleiades surrounded by wispy clouds of gas and dust. Nearly two decades ago, scientists discovered that those clouds are not associated with the stars themselves but are part of an independent nebula that crashed into the Pleiades.
White now finds that a second gas cloud is bombarding the cluster, creating a slow-motion pileup 400 light years from Earth. Astronomer Steven Gibson of the University of Calgary, whose observations led to the findings, says the collisions have no effect on the stars but offer astronomers a close-up view of the kind of complex interactions that happen in interstellar space. “The presence of the clouds does change the appearance of the cluster, which is enshrouded in nebulosity as a result,” he says.