That's a good question. I notice that's the only object that looks kind of 3D in the whole picture. So I am wondering whether the picture was manipulated somehow or this is a glitch in the camera, a microscopic particle? I am not an expert. It could be a space object, but what kind of? It's spherical and looks smooth - could it be one of the moons in the Solar System? Or a dwarf planet? Could it have this 3D look because it's very close to the telescope compared to other objects in the background?