To Ann (and others), my thanks for speaking up about your confusion! Misery loves company.
I wanted to teach my niece something about optical illusion and perspective, how the brain (mis)perceives dimensions and distance. So, I slowly went line by line through the accompanying explanation using supplemental gnarled hand gestures and creative analogies, only to watch my careful tutelage fall apart with the sentence "distance estimates for the Bubble Nebula and associated cloud complex are around 11,000 light-years, while star cluster M52 lies nearly 5,000 light-years away."
WTF?? How did I paint myself into a corner that even the tempting but lame offer - "let's go get ice cream" - failed to extricate?
Uncle StarDust isn't often flustered, but Science4Man's math lesson (hate higher math) further obscured the field of view like pigeon droppings on binocular lenses... until I read his completed thought.
I still hope to regain some semblance of credibility with my niece. Hopefully, someone will explain (using layman's English) how a significantly smaller-sized but larger-appearing object is twice as distant? This does not compute.
Googling "distance from earth" did nothing to help as the Bubble is still considered the more distant of the two:
- The distance of this cluster is not very well known; Kenneth Glyn Jones adopts 3,000, Mallas/Kreimer 7,000 light years, while the Sky Catalogue 2000.0 gives 5,200 (i.e., 1,600 pc) and Götz 5,050 light years. Robert Garfinkle, in his "Star Hopping", quotes about 3,000, Harvey Pennington and George Kepple and Glen Sanner's Night Sky Observer's Guide 3,900 light years. REF1- http://www.seds.org/messier/m/m052.html
NGC 7635 - Bubble Nebula
: At a distance of 7,100 light-years from Earth, the Bubble Nebula is located in the constellation Cassiopeia and has a diameter of 6 light-years. REF2- http://hubblesite.org/newscenter/archiv ... 4/image/a/