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Bode's Galaxy (NGC 3031)
Nathan Jansen

Bode's Galaxy

Bode’s Galaxy, M81, or NGC 3031; no matter what you call it, this grand design spiral galaxy is a sight to behold.  Here on earth we sit 11.8 million light-years away from M81.  Or perhaps you’re transporting cargo from Earth to M81 in the Millennium Falcon. If so, you can anticipate a 3.62 megaparsec run.  If you decide to visit bring a bear-trap; because this galaxy inhabits the Ursa Major Constellation.  If your friends are watching from home (given they live in the Northern Hemisphere), tell them to break out their binoculars and telescope; because will likely see Bode’s Galaxy with its apparent magnitude of +6.9.

Upon arrival at M81 don’t get lost!  You will find the galaxy spans across nearly 90 thousand light-years, and contains nearly 250 billion stars.  At its center you will run into a bright yellow nucleus where an old stellar population luminously resides; however, beware the black hole that sits in the center of this compact area. Next, swing out on the galaxy’s two spiral arms and swim in the blue clusters of star forming regions.  The UV emitted by hot, young stars ionizes the interstellar gas consisting of predominantly hydrogen and helium, which is then seen as red emission around these new stars.  Looking through an infrared lens will instead pick up these hotter areas as a blue color.  Your friends at home can soak in a bath of light sent by the stellar dust which handily scatters blue light away and sends the red light forward.  If you are straight on from the dust and starlight you will soak in a warm bath of red light (known as interstellar reddening); but if you are to the side of the dust and starlight you will cool off in a shower of blue light.  You may wonder why only two spiral arms dominate the galaxy.  M81 and its neighbor M82 have played a role in shaping each other, thus helping explain their current forms.

The image shown are all mosaics of two adjoining fields, as the galaxy was too large to fit in one field alone.

The image is black and white due to technical issues preventing calibration of a colored image. Multiple efforts trying different calibration schemes mysteriously failed. Afterwards, it was found that light from a blue LED on a USB cable in the observatory dome was leaking into the image. (This had originally been covered with tape, but weathering caused the tape to come loose.) While no color is present in the image, the fascinating part of this galaxy is not its color. Rather the two spiraling arms are what makes Bode's Galaxy a sight to see.

References:

"What is the interstellar medium?" (n.d.). Retrieved May 03, 2016, from http://www-ssg.sr.unh.edu/ism/what1.html

Dunbar, B. (2008). Black Holes Have Simple Feeding Habits. Retrieved May 05, 2016, from http://www.nasa.gov/mission_pages/chandra/news/08-071.html

"Messier 81". Retrieved May 03, 2016, from http://freestarcharts.com/messier-81

 

Right Ascension (J2000) 09:55:33
Declination (J2000) +68:57:17
Filters used (C) Clear
Exposure x number of images for each filter C (9s x 4)
Image dimension 1009x1245 pixels; 22.03x27.18 arc minutes
Date/time observed March 18, 2016 (UT)
Distance 3.62 Mpc ("Messier 81")
Scale 0.064 pc/arc minute

 

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