Solar System [odd one out] [words and pictures] [formation of]

the Sun the 8 planets of our Solar System Earth orbitting the Sun a spiralling galaxy planet Earth our Solar System The Big Bang the Milky Way

Within the grid there are 7 pairs of pictures and words and one ODD ONE OUT. Click on the pictures and words which you think are pairs to get rid of them. The one word or picture remaining will be the one you have chosen as the ODD ONE OUT.