​                                                          NGC6946 - The Fireworks Galaxy

 

    There are probably no more esthetically pleasing structures in nature than a spiral, and this is especially true when one looks at the many different types of galaxies. The Whirlpool galaxy, M51, is an excellent example of a spiral galaxy. Read on to learn more about this island universe.

 

    Take a close look in the constellation, Canes Venatici, which lies below the Big Dipper, and if you look below the last star of the handle of the dipper you will find Messier object, M51, or the Whirlpool galaxy. The galaxy also has the New General Catalog classification, NGC 5194. A quick look at the image above , easily demonstrates why it is known as the Whirlpool galaxy. Also evident is its companion, NGC 5195, which is intimately connected to M51.

 

    This image clearly shows the dark dust lanes that lace the arms of the galaxy. The blue color in the arms is due to the hot, blue stars (type O and B stars) that have formed in these dust-rich regions of the galaxy. The pinkish knots are star forming regions – stellar nurseries. These are creating stars that will shine on long after the short-lived blue stars that populate the arms have consumed the last of their fuel.

 

    The image also clearly shows the connection between M51 and its companion, NGC 5195, as it pulls on the arm of M51. For many years it was unknown if it was interacting with M51 or just in the line of sight behind M51. It wasn’t until observations from radio telescopes revealed that they are interacting with each other, and this interaction may have generated the density waves that contributed to the spiral structure of the Whirlpool galaxy.

 

    The Whirlpool galaxy is a classic spiral galaxy (type Sc) seen full-on, as opposed to the edge-on view typified by the Sombrero galaxy. The galaxy is about the same size as the Milky Way, 100,000 light-years across. At a distance of about 26 million light-years (I have seen distance estimates from 22 - 37 million light years on the Internet.), it shines at a magnitude of 8.4, outside the range of naked eye observation, but easily seen in a telescope (the larger the aperture, the greater the structural detail that will be visible). Interestingly enough, Messier never knew the true beauty of the galaxy, as he was only able to resolve it as a nebulous cloud in 1774. It wasn’t until 1845 that the spiral structure of the galaxy was discerned and documented by the Earl of Rosse, William Parsons, using a 72 inch reflector.