NASA (leave it to them to obfuscate the truth as always) - I feel this lends support that there is a "sun" in Uranus:
Uranus is warmer than we thought.
New computer modeling techniques revealed that Uranus generates internal heat. This is similar to our solar system’s other gas giants, like Jupiter or Neptune.
NASA, Oxford Discover Warmer Uranus Than Once Thought - NASA Science
I know, I know... So many bad jokes are possible, here but it's still interesting!