Jupiter. in the solar system in the galaxy.... Osiris ... or so far, it's the record-holder for known physical size. It's a planet orbiting the star HD 209458 in the constellation Pegasus. It is larger than Jupiter, with a radius of 1.32 times the radius of Jupiter. As far as mass, there are many planets around other stars that are up to 11 times more massive than Jupiter (Jupiter has actually a small iron core and most of it's body is hot gas), although we don't know how physically large (in radius) they are because we can only measure radius that when the planet crosses in front of (transits) the star. We know they are there, and how big they are, because of the wobble in the stars orbit. It is definitely *not* Jupiter. we have detected 157 extrasolar planets (planets around other stars in our galaxy). Most of these are more massive than Jupiter (the larger planets are easier to see). Most of these have names like HD 209458b (the first one we actually saw with a telescope). Osiris is one of the few extrasolar planets we have named (... another one is Methuselah, the oldest known planet at 12.7 billion years old). Finally, there is a limit to how big a planet can get. Anything larger than 11 times the mass of Jupiter, and fusion occurs ... it's no longer a planet, it's a star. Source: http://www.nmm.ac.uk/server/show/ConWebD... http://www.answers.com/topic/extrasolar-...

I think he was referring to our system of planets but nice google search ;)