First time since 1226: this will happen on 21st December

For the first time since 1226, Jupiter and Saturn will come close enough together to appear as a double planet, say astronomers from Rice University. The phenomenon will be visible to the naked eye in the twilight of 21st December.

American astronomers at Rice University have calculated that Jupiter and Saturn will appear very close together as a double planet on 21st December, according to a press release published on phys.org.

Alignments between these two planets are somewhat rare, occurring once every 20 years or so. However, such an alignment had never taken place since the Middle Ages, explained astronomer Patrick Hartigan:

“We would have to go back to 4th March 1226 to see a closer alignment between these celestial objects visible in the night sky.”

As Jupiter and Saturn have been moving closer together since summer, they will be separated by less than a Full Moon diameter on 21st December.

On the evening of the winter solstice, the “closest approach, they will look like a double planet separated by only 1/5 of the diameter of a full moon,” says the astronomer.

Place and time of observation

Although the best viewing conditions are near the equator, the event will be visible from anywhere on Earth, weather permitting. The planets will appear low in the sky for about an hour after sunset each evening during the aforementioned period, said Hardigan.

According to the astronomer, the next time they are aligned so closely will be 15th March 2080. Then the phenomenon will not recur until 2400.