SUMMARY: An Australian astronomer has discovered 20 galaxies that contain mostly gas, rather than stars - revising the definition of "galaxy". These galaxies are giant discs of gas, tens of thousands of light-years across, and contain the mass of billions of sun, but for some reason their hydrogen hasn't coalesced into stars like regular galaxies. The discovery of these gas galaxies will help astronomers better understand what it takes for a galaxy to form.
Comments or questions about this story? Feel free to share your thoughts.