Jupiter and Saturn to get medieval in December phys.org

Just after sunset on the evening of Dec. 21, Jupiter and Saturn will appear closer together in Earth's night sky than they have been since the Middle Ages, offering people the world over a celestial treat to ring in the winter solstice.

"Alignments between these two planets are rather rare, occurring once every 20 years or so, but this conjunction is exceptionally rare because of how close the planets will appear to one another," said Rice University astronomer Patrick Hartigan. "You'd have to go all the way back to just before dawn on March 4, 1226, to see a closer alignment between these objects visible in the night sky."