Astro-Shed

With every spring comes what Astro imagers call “Galaxy Season.” This is the one time when our little planet’s orbit around its sun allows us to look perpendicular to our home galaxy’s disc during the night-time hours. Looking perpendicular to the Milky Way’s disc reveals an area of space where galactic dust and stars no longer hide faint galaxies. The constellations of Leo, Virgo, Cannes Venatici, Coma Berenices, and Ursa Major all contain a trove of hidden galaxies, if you no where to look.

This week’s target was Messier 109, a beautiful barred spiral galaxy, located just to the South-East of Phad, or Gamma-Ursa Major. M 109, also known as NGC 3992 was discovered by Pierre Mechain in 1781. It was not included in Messiers original list of 103 objects until the list was revised and finalized in the 1970’s.

M 109 is the largest of the M 109 local group of galaxies. The group is actually split into a Northern and Southern Group. The Northern group is centered on M 109 and contains about 30 members. M 109 itself has three companions, two of which are visible in this image.

The Southern group is to the South East, about halfway between Ursa Major and Cannes Venatici. It contains fewer but brighter galaxies than the Northern group.

The image of M 109 captured here shows a nearly face-on barred spiral galaxy. The color of the central bar is influenced by older stars whose colors are in the yellow to red range. It may also be influenced by a high dust content which cause a stars light to shift more towards the red end of the spectrum.

The spiral arms are where the younger stars live as indicated by their bluish color. If you look closely at the spiral arms you will also notice tight little knots or condensations. I liken these to pearls on a string. These areas of active stellar formation where young stars are still clumped together around their birth nebula.

Towards the ends of the bars and in the spiral arm on the top left you can just detect some dark dust lanes.

Galaxy Season starts with M 109 as it is one of the first galaxies to rise in the spring evenings. This image was gathered between March 13 and 14th with my Celestron 8″ SCT and my QHYCCDMiniCam8 monochrome camera. I took 7 hours of luminance and 1 hour each of red, green and blue, 90 sec subs. I had to limit the exposures to 90 seconds as I was using 2×2 binning to achieve an optimal pixel scale that would not result in overly soft stars. If I tried to use my usual 180 sec exposure with the 2×2 binning it would have resulted in a blown out core which would not have shown the nice detail in the bar.

I look forward each year to Galaxy Season as it brings a nice break to the nebula heavy imaging of fall and winter. I hope to complete my Messier imaging project this spring. I am now down to the last 20, all being galaxies.

clear skies.