Galaxy ‘Harassment’ Noted in Study

A galaxy can really get bent out of shape if it gets harassed, a new study says.

Eventually the harassment can turn a spiral-shaped galaxy into a featureless elliptical collection of stars, researchers say.

Using a computer simulation, the researchers found evidence that a galaxy can become distorted by the gravitational pull of bigger galaxies that pass nearby at high speed. Such encounters occur about twice per billion years, and after about 3 billion years of this, an affected galaxy becomes the featureless ellipse, said researcher George Lake.

The researchers dubbed the overall process “galaxy harassment,” after rejecting the labels “galaxy pestering” and “galaxy badgering.”

It occurs only within clusters of 100 galaxies or more, said Lake, professor of astronomy at the University of Washington in Seattle. He and colleagues there and elsewhere discuss the idea in the Feb. 15 issue of the journal Nature.

Harassment would leave arcs of debris streaming out of an affected galaxy, and such arcs have been seen in images from the Hubble Space Telescope, Lake said.