The Japanese text is: ちなみにこの後陽太は初めての魔法に大興奮した(ムムは調子のった)
Running that through a translator I got: By the way, after this, Yota was very excited about the first magic (Mumu was in good shape).
I'm not sure where they got the stuff about the sun. Also, making the sun bigger would make it colder, not hotter. Gasses cool when they expand.