For a long time, people believed that everything in the sky was perfect and ordered, but we now know that things are just as chaotic up there as they are down here.
A newly released Hubble picture shows just how beautiful a mess this can be. The image shows UGC 4459, an irregular dwarf galaxy located 11 million light-years from the Milky Way in the constellation of Ursa Major (The Great Bear).
UGC 4459's stellar population is spread out (diffused) and disorganized, with clumps of young blue stars, red old stars, and extended clouds of gas shining in red. It is composed of several billion stars, and although that might seem like a lot, it's tiny compared to galaxies such as the Milky Way, which has a mass of 100 billion suns. Irregular dwarf galaxies have low rates of star formation, and due to their diffuse nature, only a small fraction of their original gas content has been compressed by gravity into new stars.
Galaxies can become irregular during mergers or by gravitational interactions with larger companions, which stretch and deform them into the messy shapes we see today.