An Archetypal Dwarf Galaxy: NGC 5477 in Ursa Major | Hubble

An Archetypal Dwarf Galaxy: NGC 5477 in Ursa Major | Hubble

The constellation of Ursa Major (The Great Bear) is home to Messier 101, the Pinwheel Galaxy. 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, one of these dwarf galaxies in the Messier 101 group, is the subject of this image from the NASA/European Space Agency Hubble Space Telescope. Without obvious structure, but with visible signs of ongoing starbirth, NGC 5477 looks much like an archetypal 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.

Distance from Earth: 20 million light years

The observations were taken as part of a project 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 has numerous galaxies in the background, including a number 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.

This image is a combination of exposures taken through green and infrared filters using Hubble's Advanced Camera for Surveys. The field of view is approximately 3.3 by 3.3 arcminutes. 

Credit: ESA/Hubble & NASA
Release Date: Jan. 7, 2013

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