In a celestial phenomenon not seen in 397 years, Jupiter and Saturn, from the perspective of observers on Earth, will appear to be aligned so closely they will almost seem to be one single "star" in the sky. Every few years, from the perspective of earthlings, the two planets seem to pass each other in the same general area of the sky and that is known as a conjunction. When the two planets align on this date, however, they will seem to be much closer, a "great conjunction" -- with only 6 arc minutes of sky separating them.

Subscribe to Guardian News on YouTube ► http://bit.ly/guardianwiressub

Support the Guardian ► https://support.theguardian.com/contribute

Today in Focus podcast ► https://www.theguardian.com/news/series/todayinfocus

The Guardian YouTube network:

The Guardian ► http://www.youtube.com/theguardian
Guardian Football ► http://is.gd/guardianfootball
Guardian Sport ► http://bit.ly/GDNsport
Guardian Culture ► http://is.gd/guardianculture