Hubble Watches Triple Galaxy Smash Up

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Is this an image of two galaxies? Actually, its three interacting galaxies that are locked in a gravitational tug-of-war. The give and take going on here may eventually tear at least one galaxy apart, and someday the three will likely merge into one super-large galaxy. This new image from the Hubble Space Telescope’s Advanced Camera for Surveys allows astronomers to view the movement of gases from galaxy to galaxy, and already, strong tidal interaction surging through the galaxies has dragged a significant number of stars away from their original homes.

The three galaxies are about 100 million light-years away, in the constellation of Piscis Austrinus (the Southern Fish). The three pictured galaxies — NGC 7173 (middle left), NCG 7174 (middle right) and NGC 7176 (lower right) — are part of the Hickson Compact Group 90, named after astronomer Paul Hickson, who first catalogued these small clusters of galaxies in the 1980s.

NGC 7173 and NGC 7176 appear to be smooth, normal elliptical galaxies without much gas and dust. In stark contrast, NGC 7174 is a mangled spiral galaxy, barely clinging to independent existence as it is ripped apart by its close neighbors. Stars are being moved away from their original locations, and are now spread out, forming a tenuous luminous component in the galaxy group.

Ultimately, astronomers believe that the stars in NGC 7174 will be redistributed into a giant ‘island universe’, tens to hundreds of times as massive as our own Milky Way.

Source: Space Telescope Institute