NGC 7318 are a pair of colliding galaxies about 300 million light years away in the Constellation Pegasus . They are members of the famous Stephan’s Quintet.
The Spitzer Space Telescope revealed the presence of a huge intergalactic shock wave, shown by the magnificent green arc in the picture at right produced by one galaxy falling into another at millions of miles per hour. As NGC 7318B collides with NGC 7318A , gas spread throughout the cluster, atoms of hydrogen are heated in the shock wave , producing the green glow. The molecular hydrogen seen here is one of the most turbulent forms of molecular hydrogen ever seen. This phenomenon was discovered by an international team of scientists of the Max Planck Institute for Nuclear Physics (MPIK) in Heidelberg. Most notable is the fact that this collision can help provide a view into what happened in the early universe 10 billion years ago when it formed.