Galaxies
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A Deep View of Messier 83: The Southern Pinwheel Galaxy
With nearly 70 hours of exposure I wanted to show the majestic barred spiral Messier 83 in all its glory. Visible here is the large halo extending far beyond the bright spiral arms, including sections of the northern stream that curves from the 10 o'clock position and outside the field of view, then enters the field again in the 2 o'clock position behind the bright blue star.
The colourful spiral itself is filled with bright red HII regions, enhanced here with 4.25 hours of H-Alpha exposure. Intricate swirling dust lanes trace the spiral arms and merge in a central maelstrom near the bright warmly glowing core.
To the left (East) of Messier 83 lies two smaller galaxies PGC 724525 and PGC 48132. These are much further away but show some interesting structures, particularly the upper one has several tidal tails that make it look like a tiny Star Wars TIE Fighter.
Visible near the top right is the small and faint dwarf galaxy dw1335-29 which was confirmed to be a companion of Messier 83 in 2018.
Messier 83 is classified as being an intermediate between normal and barred spiral galaxies. It is located in the southern constellation Hydra and is one of the show pieces of the southern sky, often referred to as The Southern Pinwheel. The distance to M83 is estimated to be some 15 million light years.
M83 is an example of a 'grand design' spiral galaxy with strongly defined spiral arms and shows many pink and blue knots throughout the spiral structures. The pink regions are massive gaseous nebulae in which new stars are born. The blue regions represent young stellar populations which have formed relatively recently within the last dozens of million years. Between the pronounced spiral arms are regions with fewer stars. Noticeable dark dust lanes follow the spiral structure throughout the disk, and can be traced well into the central region to the nucleus. Around the nucleus is an older population of yellow stars which dominates the whole central region, and extends along the bar-like structure.
The arms do not rigidly follow the rotation of the galaxy, but are instead areas of higher density that tend to form in self-gravitating systems. The large amount of bright blue supergiant stars that define the spiral pattern indicate where star formation is taking place, and it is evident that the star formation rate is higher along the leading edge of the spiral arms, as predicted by density wave theory. All the stars, gas and dust follow individual orbits around the galaxy's centre, occasionally moving through a dense spiral arm area where the increased density triggers the birth of new stars. Of those, bright hot blue supergiants shine the brightest but also live the shortest lives, and therefore die before their orbits have carried them far from the arms. Hence the luminous shape of the arms is continually preserved.
Scattered throughout the field of view far in the distant background lie many other galaxies; some up to several billion light years away and visibly reddened by the relativistic redshift caused by the expansion of the Universe.
Image details:
Date: 17 nights, March - August 2020
Exposure: HaLRGB: 255:2693:380:370:370 mins, total 67 hours 48 mins @ -25C
Telescope: Homebuilt 12.5" f/4 Serrurier Truss Newtonian
Camera: QSI 683wsg with Lodestar guider
Filters: Astrodon LRGB E-Series Gen 2 and 3nm H-Alpha
Taken from my observatory in Auckland, New Zealand
Plate solve:
Resolution ............... 0.764 arcsec/px
Rotation ................. -1.404 deg
Focal distance ........... 1457.19 mm
Pixel size ............... 5.40 um
Field of view ............ 41' 57.1" x 31' 34.9"
Image center ............. RA: 13 37 00.726 Dec: -29 51 53.05
