We saw this image at the beginning. Let me emphasise: it was taken on a fixed tripod. Stars do not trail, even in the 100% inset, because the rules were followed:
The greenish blob in the inset is a comet. There are often a few comets around that can be photographed like this. They are not spectacular, being small and having no tails - unlike comets in photos you may have seen. The spectacular ones are quite rare.