Credit: NASA, ESA, K. Kuntz (JHU), F. Bresolin (University of Hawaii), J. Trauger (Jet Propulsion Lab), J. Mould (NOAO), Y.-H. Chu (University of Illinois, Urbana), and STScI

Galaxies are among the largest structures in the universe. But some galaxies, such as Messier 101, are giants among smaller giants.

M101, also called the Pinwheel Galaxy, is considered a giant galaxy and is best known example of a “grand design spiral.” Explore the mirrored spiral arms as they curve away from the bright galactic core in this image from NASA‘s Hubble Space Telescope. The face-on spiral galaxy shows us vast regions of star-forming nebulae, brilliant, blue areas of new stars and lanes of dark dust. Thick dust and gas give M101 the fuel it needs to create new stars far into the future. M101 is nearly twice as large as our Milky Way. As you move from one side of this galaxy to the other, you will cross 170,000 light-years. Astronomers estimate that the galaxy contains more than 1 trillion stars. Explore also dozens of distant background galaxies seen in the image.

The Pinwheel Galaxy lies just a stone’s throw away, about 25 million light-years from Earth toward the constellation Ursa Major, the Great Bear. Light that we’re seeing from this galaxy has been traveling for 25 million years to reach our eyes here on Earth. When the light rays left M101, Earth was cooling into a series of ice ages, mammals were flourishing along with many modern birds, and whales were appearing in the oceans along with modern sharks.