NGC 6240 is a galaxy. Well, almost a galaxy: it's actually two galaxies that have collided and are well on their way to merging and becoming one galaxy.

When two galaxies collide like this, it's very rare for stars to physically smack into each other. But the gas and dust clouds are light years across, and encounters are inevitable (resistance, as they say, is futile). When they do the protean galaxy undergoes a burst of star formation, blasting out light and creating scads of dust.

This image, like the galaxies that make it, is the merging of two shots from Spitzer (colored red) and two from Hubble (green and blue). The red is dust, and you can see how turbulent and chaotic the collision is. In a few million more years the action will be over, and what will remain is a single, large galaxy. Our own Milky Way probably suffered several collisions like this in its 12-billion-year history.

Original blog post
Original press release
Image credit: NASA/JPL-Caltech/STScI-ESA