A Giant Among Giants

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.