Hubble captures a dwarf galaxy in Messier 101 cluster

Posted by Thomas Anderson

The constellation of Ursa Major (The Great Bear) is home to Messier 101, which astronomers have dubbed the Pinwheel Galaxy.

Messier 101 is one of the biggest and brightest spiral galaxies in the night sky. However, like the Milky Way, Messier 101 is not alone, with smaller dwarf galaxies in its immediate neighborhood.

NGC 5477, one of these dwarf galaxies in the Messier 101 group, is depicted in the image above, captured by NASA's Hubble Space Telescope.

Without obvious structure, but with visible signs of ongoing star birth, NGC 5477 looks much like a typical dwarf irregular galaxy. The bright nebulae that extend across much of the galaxy are clouds of glowing hydrogen gas in which new stars are forming. These glow pinkish red in real life, although the selection of green and infrared filters through which this image was taken makes them appear almost white.

The observations were taken as part of an initiative to measure accurate distances to a range of galaxies within about 30 million light-years from Earth, by studying the brightness of red giant stars.

In addition to NGC 5477, the image above showcases numerous galaxies in the background, including some that are visible right through NGC 5477. This serves as a reminder that galaxies, far from being solid, opaque objects, are actually largely made up of the empty space between their stars.