Happy, Sneezy, Dopey, … No, no … Balin, Bifur, Bofur, … No, not them either. This post is about one of the dwarf galaxies that is part of the M101 group. Ursa Major (The Great Bear) is home to Messier 101, the Pinwheel Galaxy. Messier 101 is one of the biggest and brightest spiral galaxies in the night sky. Like the Milky Way, Messier 101 is not alone with smaller dwarf galaxies in its neighborhood. NGC 5477, which is the main subject of the Hubble Space Telescope image above, is one of those companion galaxies. It’s a typical irregular dwarf galaxy with no obvious structure but plenty of signs of new star creation. The bright nebulae that extend across the galaxy are clouds of glowing hydrogen gas in which those new stars are forming. These glow pinkish red in real life, but appear white in this false color image which was taken through green and infrared filters using Hubble‘s Advanced Camera for Surveys. The field of view is about 3.3 arcminutes wide.
The picture includes numerous galaxies in the background; some are visible right through NGC 5477. This demonstrates that galaxies, far from being solid, opaque objects, are actually largely made up of the empty space between their stars.
Image Credit: NASA