Here I present Messier 100, a beautiful grand design spiral galaxy. M100 is located in the Virgo Cluster and from our point of view, in the constellation of Coma Berenices.

The galaxy is thought to have an diameter of approximately 107,000 lys. and contain up to 400 billion stars. That would make it similar in size to our Milky Way. (the foregoing information was obtained from Messier-Objects.com).

This is a point of interest of mine. I have seen some accounts of the diameter of the Milky Way expressed as 180,000 lyrs and also, 100,000 lyrs. and other values ranging between those two figures. Estimates of the number of stars contained also vary widely. It's no surprise of course, considering it is hard to measure something like this when you are actually in it, right? But I find it frustrating when I see the differing values in the same published article.

So in giving this some thought, I believe coming up with diameters or radii of galaxies is a daunting task. Sure, you measure from the center of the galaxy for example, but what do you measure to? The "end of a galaxy" would be a rather tenuous thing I would think. Perhaps that explains why there are always differing values for the sizes and quantities of stars in the published works. Maybe a calculation of stars located within a certain volume of space is a way to define what constitutes the end of a galaxy and the beginning of extra galactic space? Perhaps there is an accepted definition for this, or maybe several accepted definitions...

To that end, I wanted to try to illustrate the tenuous nature of the outside fringes of this galaxy and thought that showing it in RGB, Monochrome, and inverted monochrome might help show the nature of the "end of a galaxy". My unscientific, unsubstantiated, purely observational conclusion would be that it is likely that galaxies are much bigger than what is commonly thought.

I hope you like this, clear skies and good health to you all...