The Doctor, the Widow and the Wardrobe - S7-E1
Factual error: Cyril is introduced looking at the Moon with a telescope... in a brightly-lit room through a window with the curtains mostly shut, circumstances in which he's not going to see anything at all. (00:03:56)
Chosen answer: 1) When Stephen Moffat took over he ignored a lot of what had been developed before (there is not in-universe answer). 2) It would have killed Rose, so the Doctor absorbed the energy. His body regenerated before the energy could do a significant amount of damage that would prevent regeneration.