Hi,

 

Well, talking about this question is pretty absurd, but as you have mentioned it, i would not let you down.

 

So, if the sheet is reflecting, the temp of sun would rise very much. As a result all the hydrogen present would fuse at the same time. Thus, large amount of energy would be produced and hence an explosion would occur which would be enough to gulp the solar system.

 

If the sheet is perfectly absorbing, then there would be no effect on the sun, but surely, it is beyond the scope of words to tell what would happen to us !!!!