Last night we had unexpected clear skies. The forecast called for partly cloudy skies, but as the sun began to set the remaining wisps of clouds in the upper atmosphere dispersed and much to my delight it was clear from horizon to horizon. I kept glancing out the window as Venus and Jupiter began to emerge as twighlight took over. Slowly, the brighter stars began to appear and as the sun’s glow to the west faded the fainter stars began to emerge… and still, no clouds in the sky. At around 10:30pm as Astronomical Twilight ended (the time of night when it becomes truly dark) I set up my tripod and equatorial tracking mount in the back yard and sighted in on a target that I had not previously photographed.
Messier 101, commonly known as the Pinwheel Galaxy, is a beautiful grand design spiral galaxy located 25 million light years away. In other words, the photons that my camera sensor captured last night were emitted by this galaxy 25 million years ago and traveled through space at over 186,000 miles per second for that entire time until it reached us here on earth. Personally, I am unable to fathom these numbers let alone try to appreciate the size and scope of our universe, and the more I learn about the night sky and the objects found within, the more I am captivated and awestruck.
M101 was discovered by Pierre Méchain in 1781. How these amazing astronomers found these deep space objects with the technology available at the time is truly quite incredible! I often wonder what it must have been like to view these objects for the first time over 230 years ago against a backdrop of the scientific understanding of the universe at the time. Pierre was the son of a ceiling designer and plasterer and displayed mental gifts in mathematics and astronomy, but despite his acuity and interest in the night sky could not pursue his studies due to a lack of money. He eventually persevered with his passion of space and along with friend Charles Messier was an early contributor to the study of deep space objects. It is also worth noting that Pierre was born on August 16th (1744), and shares a birthday with yours truly.
You can find M101 near the end of the handle of the big dipper in the constellation Ursa Major. If you draw an equilateral triangle from the two end stars of the handle towards the same side as the opening of the “dipper” you will find the approximate location. The Pinwheel is invisible to the naked eye, however with a long camera exposure it is able to be recorded. Its spiral arms extend out to encompass a space in the sky of 25 minutes, giving it an apparent diameter of just less than that of the full moon.
Notice that there is some asymmetry with the spiral arms of M101. It is believed that this is due to a near collision with another galaxy, and that this event caused density waves in the spiral arms to be amplified, compressing hydrogen gas and leading to bursts of star formation. -(Jerry Lodrigus) There are bright pink and red knots of ionized hydrogen gas within the spirals, however I was unable to capture this detail with this attempt. I did not use my light pollution filter, and as a result the RAW files had a strong orange red hue to them. Removing this cast, also removed the ionized hydrogen gas. Perhaps I will combine this image with some frames using my light pollution filter to recover this detail.
Canon T5i (Modified), Canon 300mm f2.8is II + Canon 1.4X TC III (420mm), f4, 75 second exposures (62 for a total of 77.5 minutes exposure), ISO 1600, Astrotrac, ImagesPlus, Photoshop, Lightroom. 144 Light Frames, 28 Dark Frames, 30 Bias Frames, 26 Flat Frames