APOD 4.3

For this week's APOD, I chose the picture called Messier 101.  It is a picture of a big spiral galaxy M101, and it was in Charles Messier's catalog towards the end.  This image is actually a mosaic of pictures, put together by the Hubble Observatory.  Ground-based data was needed as well in order to define the red emission in the galaxy's star-forming regions.

This particular galaxy happens to be a rather huge one.  To be more exact, it spans about 170,000 light years across, and is approximately 27 light years away.  This means that it is about double the size of our Milky Way Galaxy. It can also be called the Pinwheel Galaxy 101, and is located in the boundaries of Ursa Major, which is about 25 million light years away.  The image shows dust and stars within the galaxy, along with background galaxies.   In addition to being in Messier's Catalog, this spiral galaxy was also recorded by Lord Rosse's telescope, the Leviathan of Parsontown.  The galaxy is in the M101 group, which contains about nine other galaxies, with this particular galaxy being the brightest.  The visual brightness of Messier Object 101 galaxy is a 7.9 magnitude.