Closest since Galileo's time, Jupiter and Saturn to form 'Great Conjunction' on Dec 21 | How to watch

In a rare sight, Jupiter and Saturn will merge in the night sky on Monday, December 21, appearing closer to one another than they have since Galileo's time in the 17th century. The union of Jupiter and Saturn on December 21 is known as the 'Great Conjunction'. The National Aeronautics and Space Administration said it’s been nearly 400 years since the planets passed this close to each other in the sky, and nearly 800 years since the alignment of Saturn and Jupiter occurred at night, as it will for 2020, allowing nearly everyone around the world to witness this 'Great Conjunction'. Thirteen years later, in 1623, the solar system’s two giant planets, Jupiter and Saturn, travelled together across the sky.