You are right about the over-exaggerated diameter of the largest stars known. The press release at
www.lowell.edu/press_room/releases/recen...argest_star_rls.html
says that the current candidates would just engulf Jupiter's orbit. Of course the outer layers of these stars would be extremely tenuous and not far off the general density of the inter-planetary medium.
Thank you skynotes. I read the page and then added it to my favorites. It got me thinking about why these stars are so large. They're not the most massive, the coolest, or the brightest. It's sort of hitting the sweet spot, and that got me wondering if a very massive star might go through a very short super-large phase. Because they would be so rare, and this size would last such a short time, it may be that we don't find any super-biggies because there are none. At the moment.
  