A photograph of an object does not necessarily look the same as the real object. There are various optical imperfections, which are impossible to avoid by both the designer of the optical system and the photographer taking the picture. One of those imperfections causes lens flare.
Some flat-Earthers noticed the existence of a ‘mysterious celestial body’ next to a photograph of the Sun or the Moon. They would use such sightings to ‘explain’ various celestial phenomena which cannot be readily explained in the flat Earth model, like eclipses. They are wrong. The ‘mysterious celestial body’ was merely a lens flare.