An Irregular Mystery

Galaxies are massive collections of stars, gas, and dust (and dark matter, too). They come in four basic shapes: spiral (like our Milky Way), elliptical, peculiar, and irregular. Irregulars are pretty much like the name says: They tend not to have an overall structured shape, but are, well, irregular. Still, despite that, some do have a semblance of shape, and it's not always clear why. Take IC 3583, for example. That's the galaxy above, in a gorgeous Hubble Space Telescope image. It's definitel...