HUBBLE SPACE TELESCOPE, LOW EARTH ORBIT
This assembly of galaxies is the Hickson Compact Group 40. The prominent orange bands in the spiral galaxies are dense clouds of interstellar dust packed full of gases, and it’s in these dusty regions where star formation is active.
These galaxies, pictured by the Hubble Space Telescope, are held together in a gravitational dance and they are so densely packed that they could fit in an area twice the span of our own Milky Way’s disk.
Astronomers don’t know for sure why these galaxies are so tightly bound, but it’s possible that dark matter, a mysterious – and so far, invisible – form of matter, may play a role.
When galaxies come together, dark matter can form a big cloud around the group. As the galaxies plough through this cloud, gravitational effects act like a frictional force and slow their motion. This causes the galaxies to lose energy and they fall together.
Scientists estimate that in around one billion years, these galaxies will eventually collide to form one giant, elliptical galaxy.