Credit: Courtesy of the THINGS survey team
Composite image of the gas-rich dwarf spiral galaxy IC 2574. Atomic gas is depicted in blue , older stars are in orange , and young stars are shown in purple . The horizontal green bar shows a physical scale of 15,000 light years; this corresponds to about half the distance between the Sun and the center of the Milky Way. IC 2574 is not part of McGaugh’s galaxy sample, but it illustrates how the baryonic mass of some galaxies is completely dominated by atomic hydrogen.