If he is sure ... personally, thinking to the nature of the "Three Kings" [ancient "astronomers"] I tend to think more to something they noted in the sky. But probably it was a backwards reasoning. The tale in the Gospels is not that easy to prove, to say the least. If we had a reasonable certainty about when Jesus was born [and we haven't got it, there is who even doubts that Jesus existed ...], we could infer to which celestial phenomenon the authore of the Q Gospel [the original one] was thinking when he added the tale of the three personages looking for Jesus.
The gospel tale is silly. First, Jesus wan’t born in Bethlehem. That was just an invention, like others, to “fulfill prophecy.” Furthermore he was lowly born. No way kings or anyone else of importance would travel to see him.
To be alien [a part being Mexican, from an American perspective!] it's enough you are a member of a living species which has evolved on an other planet [or moon], not on Earth. If you settle on Mars, your sons won't be alien, since the human species evolved here ...
Skeptics, headlanders and the ill-informed have been saying that disk-shaped craft originated with Kenneth Arnold mentioning the crescents as like "saucers skipping across water" (or something like that), and claim that the later disks seen were the result of misinterpreting the shape of Arnold's objects.. I have lost track of how many VERY old disk-shaped craft reports I have posted --from the Sternenschiff of 1851 to the one from 1912, above, they aren't new ---thus their appearances in Medieval art.