This image of the nearby spiral galaxy Messier 101 (M101), also known as the "Pinwheel Galaxy", was taken during 2 orbits of GALEX on June 20th 2003. This picture is a combination of GALEX images taken with the FUV (colored blue) and NUV detectors (colored red).

The ultraviolet emissions detected by the FUV detector on GALEX shows the presence of hot young stars, formed 10 million years ago, concentrated in the tight spiral arms. Older stars, those that formed over 100 million years ago, are brighter in the NUV image than then FUV and are spread more evenly across the disk of M101. Because these older stars would also have formed in the tight spiral arms, the older stars trace the movement of the spiral arms over the last 100 million years.

This combined FUV and NUV image taken by GALEX can be interpreted as a short and medium length "exposure" of the evolution of star formation in the spiral galaxy M101. The red stars in this image are foreground stars in our own Milky Way galaxy.

From the GALEX Image Gallery

More info on this image (GALEX/Caltech)

This is a three color image of M101, a combination of GALEX images taken with the FUV and NUV detectors, colored blue, and two images in visible light from the Digital Sky Survey (colored green and orange). The UV light observed by GALEX is concentrated in the spiral arms of this galaxy and shows the presence of young stars (only 10 million years old). The more diffuse green visible light traces stars that have been living for more than 100 million years. The red visible light image shows the stars that formed over a billion years ago.

This image traces the evolution of star formation in M101 and shows the impact GALEX observations will have on the study of galaxy formation and evolution.

From the GALEX Image Gallery

More GALEX images

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Hartmut Frommert
Christine Kronberg
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Last Modification: 19 Dec 2003