I am extremely perplexed about something. I recently watched a fascinating video on YouTube comparing the sizes of the Earth, Sun, Rigel and VY Canis Majoris:

 

 

And I was curious what the actual mass of VY Canis Majoris was, and wherever I looked it was listed as only about 30 times as massive as the Sun! If the video is anything to judge by, Canis Majoris dwarfs the Sun the way the Sun dwarfs your average asteroid, so I can't fathom that this is an accurate assessment of the mass of this star. Am I overlooking some elementary factor here?

canis majoris is a red supergiant, so while its mass is only x30 our sun its density would be a lot less.

 

http://en.wikipedia.org/wiki/VY_Canis_Majoris

It has an average density of 5 to 10 mg/m³.

 

http://www.universetoday.com/94252/characteristics-of-the-sun/

Density of the Sun: 1.622 x 10⁵ kg/m³