Messier 101 (also known as NGC 5457) is a stunning face-on spiral galaxy about 22 million light-years away in the direction of the constellation Ursa Major. Hubble's visible-light view shows off luminous swirling spirals of bright stars and glowing gas that give M101 a classic spiral look. It is no wonder it has been dubbed the "Pinwheel Galaxy."
This galaxy is similar to our own Milky Way galaxy, except M101 is nearly twice the size. The section of M101 shown here is 22,500 light-years across, while the entire galaxy is on the order of 114,000 light-years across.
In this unique black and white Hubble Space Telescope image, bright knots of glowing gas highlight regions of active star formation. These star forming regions are concentrated in M101's spiral arms along with brilliant clusters of hot, newborn stars. The softer, less-bright areas near the core and between the arms consist mainly of old stars. The dark dust lanes, also visible in the image, are colder and denser regions where interstellar clouds may collapse to form new stars.
This image was made using Hubble archival data taken with the Advanced Camera for Surveys in 2002-2004. The image is a combination of two types of data: images taken with broad band blue, visible, and infrared filters show the stars while the glowing hydrogen gas is revealed in a narrow band filter designed especially for that purpose. The combination of different types of observations taken at multiple wavelengths is essential to the complete understanding of any celestial object.
Acknowledgment: R. Chandar (University of Toledo) and K. Kuntz (JHU/GSFC)