The spiral arms of the nearby galaxy
Messier 81 are highlighted in this NASA
Spitzer Space Telescope image. Located in the northern constellation of
Ursa Major (which also includes the
Big Dipper), this galaxy is easily visible through binoculars or a small telescope. M81 is located at a distance of 12 million light-years.
Because of its proximity, M81 provides astronomers with an enticing opportunity to study the anatomy of a
spiral galaxy in detail. The unprecedented spatial resolution and sensitivity of Spitzer at
infrared wavelengths show a clear separation between the several key constituents of the galaxy: the old stars, the interstellar dust heated by star formation activity, and the embedded sites of massive star formation. The infrared images also permit quantitative measurements of the galaxy's overall dust content, as well as the rate at which new stars are being formed.
The NASA website hosts a large number of images from the
Soviet/
Russian space agency, and other non-American space agencies. These are not necessarily in the public domain.
The
SOHO (ESA & NASA) joint project implies that all materials created by its probe are copyrighted and require permission for commercial non-educational use.
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Removed border from TIFF file, then converted to JPEG, from http://www.spitzer.caltech.edu/Media/releases/ssc2003-06/ssc2003-06c.shtml (http://ipac.jpl.nasa.gov/media_images/ssc2003-06c.tif).