Astr112 Photography Projects, Spring 2005

M101, Teresa Cramer

March 27, 1781 Pierre Méchain discovered Galaxy M101, also known as The Pinwheel Galaxy. Galaxy M101 is the brightest galaxy in the M101 Galaxy Group located in the Ursa Major constellation. M101 is located 22 million lightyears away and the linear size is 74,000 lightyears across. The large size of M101 creates a large gravitational pull which distorts smaller nearby galaxies.Containing a small bulge and clumpy loose spiral arms, the galaxy is classified as a Sc spiral galaxy.

As seen in the image above, M101 contains many blue regions in the spiral arms. These areas are where new stars are formed. Density waves rotate around the disk and compress with gas and dust in the spiral armes to begin star formation. The spiral arms do not last as long as the bulge because the newly formed high mass blue stars have a short life cycle. Therefore, the bulge is the oldest part of the galaxy which is indicated by the yellowish coloring.

References:
http://seds.lpl.arizona.edu/messier/m/m101.html
http://antwrp.gsfc.nasa.gov/apod/ap970805.html
http://www.noao.edu/outreach/aop/observers/m101.html
http://www.astr.ua.edu/gifimages/m101b.html