Google celebrates Johannes Kepler’s 442nd birthday. Yes, 442nd. Great space scientist. Celebrity historical. You know the drill by now, eh?
Most plot-viable bit of the first article, explained more in the second: he was born “to a mercenary father and a mother who was a healer and herbalist and was at one point tried for witchcraft.”
Okay, it’s more of a Warhammer plot, but still. Save a suspected witch, revolutionise science into the bargain!
Throw in seeing the Great Comet of 1577 when he was five and a half, perhaps?