A Pinwheel In The Sky

By The Old Farmer's Almanac
Sep 21, 2017
A Pinwheel in the Sky - M101

The Pinwheel Galaxy by David Rankin

David Rankin


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I've been cooped up inside looking out the window hoping for a clear night to setup my astrophotography equipment and bring you all a new image to enjoy.

Unfortunately this time of year in the Southwest, like much of the rest of the country, brings in a lot of storms. This has really put a damper on my ability to explore space. Luckily the other night we had a brief high pressure system setup over Southern Utah and I was presented with some very nice dark skies. It was a great night for imaging, and to test out some new photography equipment! Always a steep learning curve, but the potential of this new setup has me excited. 

Springtime is galaxy time! The direction we are looking out into space at night changes with the seasons. In the summer months the darkest part of night has us pointed right towards the center of our own galaxy, the Milky Way. On the other side of the sun, winter, night falls in the opposite direction still looking at our own galaxy but now away from the center towards the Perseus Arm. While summer and winter afford opportunities to image beautiful nebulae within our home galaxy, spring and fall have us pointed right up or down out of the galactic disc. These seasons bring the opportunity to image other distant galaxies. 

The Pinwheel Galaxy, (Messier 101)
Click here to enlarge this picture!

Credit: astrophotographer David Rankin
Technical mumbo jumbo: Atik 314L+ Mono, Atals EQG, Nautilus FW + LRGB Filteres, LRGB 78:32:32:32, 304mm F4 OTA.

There is no up and down in space. There is no right, left, forward or backward. We experience all of these things relative to our own earth and solar system. In space, galaxies can be oriented any which way. Some are displayed beautifully face-on like the Pinwheel Galaxy above, and others appear as very thin lines because we are peering into them edge-on. Most galaxies look like dinner plates, they are wide and flat, but very thin relative to their width. So with that in mind, it is easy to figure out why we see the Milky Way as a big white stripe in the night sky. 

Imagine our home galaxy as a dinner plate, and earth as a single atom within that plate. What perspective do you have of the plate from that point of view? You have an edge-on view of the plate circling around you. This is why when you find a very dark location in summer or winter, the Milky Way appears as a “stripe” across the sky. That stripe is our home dinner plate, and we are the atom within it. So while the Milky Way looks very similar to the Pinwheel Galaxy above, we will probably never be able to see it from that point of view. 

Where was this shot?

Messier 101 is a face-on galaxy located near Ursa Major (The Big Dipper) at a distance of about 21 million light years away. These galaxies are very large objects. Each galaxy can be over 100,000 light years across and contain over 200,000,000,000 individual stars. There are more stars in all of the galaxies of the visible universe than grains of sand on all of the ocean's beaches combined.


About This Blog

Welcome to “This Week’s Amazing Sky,” the Almanac’s blog on stargazing and astronomy. Bob Berman, longtime and famous astronomer for The Old Farmer’s Almanac, will help bring alive the wonders of our universe. From the beautiful stars and planets to magical auroras and eclipses, he covers everything under the Sun (and Moon)! Bob, the world’s mostly widely read astronomer, also has a new weekly podcast, Astounding Universe

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