M 101 - Pinwheel Galaxy
M 101 was discovered by Pierre Méchain in the year 1781. The large spiral galaxy is about 22 million light years away and can be seen face on. It is a good example for a "Grand Design" spiral interacting with some neighbored galaxies. Its diameter is nearly twice as large as our own galaxy. The blue areas in the spiral arms indicate regions of extended star generation whereas the red dots mark HII regions. Some of these objects have own NGC numbers. M 101 has a low surface brightness and is therefore difficult to observe - either visually or photographically.
Numerous distinct galaxies can be seen in the images located far in the background of M 101 - some of them are at least 2-4 billion light-years away.