This is possibly the most mysterious and interesting painting i've ever seen (well, technically "found" on the internet) Not much information is available regarding it's background besides being painted by dutch artist Aert De Gelder in 1710, who was a pupil and a devoted follower of Rembrandt.
The Baptism of Christ by Aert De Gelder, 1710
But Aert de Gelder's painting is not the only one to depict U.F.O. in biblical religious painting. Carlo Crivelli's Annunciation with St.Emidius preceded Baptism of Christ. Painted in 1486, it depicts a flying object similar to the one in Gelder's painting. It was easy to point it as a U.F.O. because of the iconic shape we are now familiar with thanks to endless viewing of 50's sci-fi B-Movies and of course, Steven Spielberg.
Annunciation with St.Emidius by Carlo Crivelli, 1486
But in the 1400's and 1700's, There were no Spielbergs alike (or are there?) to visually exemplify people with the imagery of outer life. These painters seem to drew what they had seen. And what they had seen remain unchanged to what we currently know about the appearance of flying saucers.
Steven Spielberg
Check our number 3, 4 and 5 for the rest of the entry!