The criteria applied to choose the Top50 are: the quality of the photo, that both the photo and its content respect and represent the Contest guidelines, and Agora's Audiovisual Team opinion.
Stars are now only used for gaining visibility within the community and increasing your chances of making the Top 50. However, a photo that has more Stars than another photo won't be chosen over it based on that factor.
The selection of the Hero depends solely on the votes of the community. The photographer whose photo has the most Votes, will become the Hero of the Contest.