Unsure what you want to explain or what your nine year old already knows, but generally I would start by explaining to him/her/them that these are pictures of very far away and enormous objects taken from a telescope that is located further away than the moon.
The telescope takes pictures in a different frequency band, like an infrared camera. These pictures are then color mapped to blue, green yellow and other colors that you normally see because just black and white image are boring to look at.
