M83 (Southern Pinwheel Galaxy)

I really love this galaxy! It’s always been a favorite, and I hope you love it as well!
M83, also known as the Southern Pinwheel Galaxy and NGC 5236, is a barred spiral galaxy approximately 15 million light-years away in the constellation borders of Hydra and Centaurus.

Nicolas-Louis de Lacaille discovered M83 on February 23, 1752 at the Cape of Good Hope. Charles Messier added it to his catalogue of nebulous objects in March 1781. It is one of the closest and brightest barred spiral galaxies in the sky and is visible with binoculars. Its nickname of the Southern Pinwheel derives from its resemblance to the Pinwheel Galaxy (M101).

M83 is a massive, grand design spiral galaxy. The peculiar dwarf galaxy NGC 5253 lies near M83, and the two likely interacted within the last billion years resulting in starburst activity in their central regions.

The star formation rate in M83 is higher along the leading edge of the spiral arms, as predicted by density wave theory. NASA's Galaxy Evolution Explorer project on April 16, 2008 reported finding large numbers of new stars in the outer reaches of the galaxy—20 kpc from the center. It had hitherto been thought that these areas lacked the materials necessary for star formation.

I couldn’t find much on the two small galaxies to the left of M83. They are designated as PGC724525 and PGC48132. I did find a discussion where a gentleman named Allen did some calculations. I’m sure there have been some new calculations, but Google failed me.

“I wanted to find out how big the larger of the 2 small galaxies is compared to our own Milky Way.
I did some quick scaling by printing the picture of M83 & the little galaxies on one page.

I measured 110mm wide for M83 & 10mm wide for the largest of the 2 small galaxies.
Those galaxies are about 600 million light years away. M83 is 15 million light years away, therefore it appears 600/15 = 40 times apparently smaller.
Given that M83 is half the size of our Milky Way lets double its size to 220mm and also multiply 40 x 10 mm = 400mm. If we divide 400mm/ 220 mm = 2. Therefore the larger of the 2 tiny galaxies is twice the size of our Milky Way galaxy & therefore about the same size as Andromeda. It's a large galaxy indeed.

[Wiki]