via Live Leak-By: weshard
It's a commonly asked question and up until recently it was thought to be VY Canis Majoris. However, recent data suggests this star is smaller than previously thought. The new monster of the heavens is NML Cygni otherwise known as V1489 Cygni.
This massive star has a radius of about 1,650 times that of our Sun. These big numbers can really be difficult to imagine. The video starts with our solar system and compares our Sun to Betelgeuse and then NML Cygni.
Betelgeuse is a red giant star in the constellation Orion. In the Northern hemisphere this is the star that makes up the hunter's shoulder in the top left of the constellation and appears red to the naked eye. Betelgeuse is so large that if you were to place it where our Sun currently is it's outer edge would reach out as far as Jupiter.
If you want to find this behemoth it resides in the constellation of Cygnus but has a magnitude of 16.6 so you would need a pretty large telescope to see it
Read more at http://www.liveleak.com/view?i=8de_1383945414#YetCkE5vRCUKLB2S.99