Credit: Unsplash/CC0 Public Domain

Google is using its logo Monday to not only celebrate the first day of winter but a rare celestial event.

The Monday doodle honors the Winter Solstice, which takes place on Dec. 21 and marks the shortest day and longest night of the year.

It also commemorates the Great Conjunction, an event during which the two largest planets in our solar system—Jupiter and Saturn—will nearly overlap to form a "double planet."

How rare is this occurrence? The last time a close conjunction of Jupiter and Saturn was seen by humans was 1226.

"Based on their orbits, from our vantage point on Earth, Jupiter and Saturn will cross within .1 degrees of each other (a fraction of the width of the full moon)," reads a description of the event by Google.

In the doodle, visitors will see Jupiter occupy one of the O's in the logo as they watch Saturn pass by and give a quick high-five.

A conjunction this close isn't expected to happen again until 2080.