If an object has M before it, that means it's from the "Messier Catalogue," when a French guy named Charles Messier was trying to look for comets, and made a catalog of the objects that weren't comets in the sky. This is the 81st object of it.
I have see this many times through my home telescope, together with M82. The image you have posted increases my enjoyment of seeing it myself - the memories and this superb image somehow work together in my mind.
Comments
This light is not visible to human eyes.
The colors in the image are "synthetic" in that they are arbitrary choices to represent the wavelengths observed.
I suspect there is a standard color scale, especially from a single telescope.
An example I have seen is Hubble (visible light) + Chandra (x-ray).
Thanks!