Question

Are there any known planets that are bigger than our sun?

Answer 1

No

Explanation:

The largest known planet is probably KOI-13b, which has a diameter just over twice that of Jupiter.

The previous record holder was WASP-17b, which has a diameter just under twice that of Jupiter.

A possible larger planet is HAT-P-32b with a diameter 2.037 times that of Jupiter, but this may be a brown dwarf.

Since Jupiter has a diameter about `1/10` of the sun, that means that the largest planets we have found have diameter about `1/5` of that of the sun.

Basically, beyond a certain mass gas giants start undergoing fusion reactions and become brown dwarf stars. Note I say mass - not diameter. As mass increases the density tends to increase too and smaller brown dwarfs tend to be similar in size to Jupiter.