Bright Infrared Images Attributed to Groups of Colliding Galaxies

Galaxies that shine very brightly in infrared images are actually groups of as many as five galaxies colliding with each other, according to astronomer Kirk Borne of NASA’s Goddard Space Flight Center. Researchers previously had believed that only two galaxies are involved in each collision. The so-called ultra-luminous infrared galaxies, shown in pictures taken by the Hubble Space Telescope, are all within 3 billion light-years of Earth, but they show what conditions must have been like shortly after the formation of the universe, when collisions of galaxies were more common.

The bright infrared glow of the galaxies is caused by a firestorm of star birth triggered by the collisions.