On the day of the winter solstice, December 21, Jupiter and Saturn will cross so closely that they will create a luminous cross that looks like a giant star from Earth.
This star is known as the "Christmas Star". In 1226, according to astronomer Patrick Hartigan, it was the last time this phenomenon was witnessed.
According to Forbes, Hartigan said:
"Alignments between these two planets are quite rare, occurring once every 20 years or so, but this conjunction is exceptionally rare because of how close the planets are going to look to each other. You'd have to go until March 4, 1226 to see a closer alignment of these planets that's visible in the night sky".
The "Christmas star" will be visible in the northern hemisphere during the entire fourth week of December.
According to experts, this astronomical event could occur again until March 15, 2080.