Today’s APOD image is fascinating on several levels.  The pair of images above are of the star Betelgeuse, a “red supergiant” (type M1-2); one at the beginning of 2019 and the other at the end of the year.  Aside from our own Sun, we generally think of stars as true “point sources” of light, having no dimension.  Even though Betelgeuse is an enormous star (if it were located where our Sun is its outer surface would be out past Jupiter), and relatively close at about 700 light-years, it is quite remarkable that our modern telescopes are able to actually resolve […]