The galaxy M101 is a 'grand design' spiral (meaning it's dominated by prominent, well-organized arms) of type Sc. Of its estimated trillion stars, many thousands of its brightest supergiants are resolved by Hubble. Click on the image for a larger view; see the text for a link to the full-resolution image.
NASA and ESA.
Today NASA and the European Space Agency released one of the the largest and most detailed photos ever seen of a spiral galaxy beyond the Milky Way. The image shows the glorious face-on spiral M101, located 25 million light-years from Earth in Ursa Major off the handle of the Big Dipper. The image is a mosaic of 51 Hubble Space Telescope frames and several ground-based shots. The Hubble images used to make this 16,000-by-12,000-pixel composite were assembled from archival data, which were taken for a variety of research projects dating from 1994 to 2003. The galaxy itself is roughly twice the size of our Milky Way and contains about 1 trillion stars.
The views above and below are cropped and relatively low-resolution. To view better versions of the whole image, visit the press release Web site.
Impressive as this picture is, it is not the largest of a galaxy ever taken. Connecticut-based amateur astronomer Robert Gendler has made a 90-hour CCD mosaic of the Andromeda Galaxy (M31) that is 21,904 by 14,454 pixels. Gendler used a much smaller aperture beneath Earth's atmosphere, but M31 is ten times closer than M101.
A detail of the M101 image, including another, much more distant grand-design spiral galaxy in the far background (at lower left edge). Click on the image for a larger view, and see the text for a link to a full-resolution view.
NASA and ESA.