Later this month, look up to see Jupiter and Saturn appear closer together than they've been since the Middle Ages

On Monday night, December 21, Jupiter and Saturn will look closer together than they've appeared since March 4, 1226, almost 800 years ago. This event, taking place on the December solstice, is known as a "great conjunction."

"On the evening of closest approach on Dec 21 they will look like a double planet, separated by only 1/5th the diameter of the full moon," says Rice University astronomy professor Patrick Hartigan. — Read the rest