APOD
Astronomy Picture of the Day
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
M101: The Pinwheel Galaxy
Explanation: Why do many galaxies appear as spirals ? A striking example is M101, shown above , whose relatively close distance of about 22 million light years allow it to be studied in some detail. Recent evidence indicates that a close gravitational interaction with a neighboring galaxy created waves of high mass and condensed gas which continue to circle the galaxy . These waves compress existing gas and cause star formation . One result is that M101 , also called the Pinwheel Galaxy, has several extremely bright star-forming regions (called HII regions) spread across its spiral arms. M101 is so large that its immense gravity distorts smaller nearby galaxies.
| Date | August 5, 1997 |
|---|---|
| Credit | Credit: W. Keel (U. Alabama in Tuscaloosa), KPNO, 4-m Mayall Telescope |
| Authors & editors: | Robert Nemiroff (MTU) & Jerry Bonnell (UMCP) |
| A service of: |
ASD at NASA / GSFC, NASA Science Activation & Michigan Tech. U. |