But, you asked about the biggest planet *outside* our solar system. We haven't directly seen or measured all the planets in the universe, so we don't know for sure which is the biggest!
However, astronomers have discovered some *very* large planets outside our solar system, called exoplanets. Some of the biggest ones discovered so far include:
* HD 100546 b: This planet is estimated to be about 6 to 16 times the mass of Jupiter.
* TrES-4: This planet is about 1.7 times the radius of Jupiter, making it very large and puffy.
* WASP-17b: This planet is about 1.9 times the radius of Jupiter, and is even more puffy than TrES-4.
It's likely that even bigger planets exist out there, waiting to be discovered!
