The Pinwheel Galaxy

Early this year, Mike Sherick pitched the idea that all of us using JMSM Observatory dedicate our time to imaging a single target. With this effort, it should be possible to acquire an exceptionally deep image that we can all then process as we'd like. After some discussion, I choose our first target to be The Pinwheel Galaxy (M101) and its neighbor NGC5474.

Mostly during the month of March, Mike, Dean Salman, Rick Wiggins, and I collected approximately 44 hours of data through Clear, Red, Green, Blue and Hydrogen-alpha filters. This is my version of the image. Click the above image to see larger versions and some of the technical details.

M101 is a beautiful face on spiral galaxy showing well defined arms and dust lanes. Its asymmetrical shape indicates a (relatively) recent interaction with a companion galaxy (maybe NGC5477 - upper right in the image). The interaction not only distorted M101's arms, but warm dust from the companion is falling into M101 and has spurred star formation causing the creation of many young, hot (blue) stars. Indeed, recent study of M101 by Japan's AKARI InfraRed telescope shows that more star formation is taking place in the outer regions of M101 than in its core. This is reverse the process happing in other spiral galaxies, like our own Milky Way, where star formation is more active in the central portion of the galaxy.

M101 is a large spiral galaxy. It is about 170,000 light years in diameter - about twice the size of the Milky Way. NGC5474 (upper left corner of the image) is feeling the pull of all this mass. It is tidally locked with M101 - which causes NGC5474 to be distorted with its core so off center.

This is the deepest view of this field that I have personally seen. The approximately 44 hours of exposure revealed details in the outer reaches of both M101 and NGC5474 that I have not found in other images. Not to say there aren't deeper images of M101, but their field-of-view is limited and does not show the extent visible here. If anyone does have an image showing the outer reaches of these galaxies, I'd love to see them to compare.

Of course there are numerous background galaxies throughout the field. Have a look around.