In the Doodle, four of the "Google" letters are topped with snow, and the two "o's" represent the planets Jupiter and Saturn. As Saturn drops down next to Jupiter in the night sky, lifts its rings and gives Jupiter a "high five," then disappears, a tiny Earth (wearing a nightcap) watches from below and jumps up and down in delight.
Google commented on their Doodle as follows:
"As Earth’s Southern Hemisphere welcomes summer and winds down from the longest day of the year [in the Northern Hemisphere, we welcome winter and wind down from the shortest day of the year], it seems Jupiter and Saturn have decided to put on quite an unusual show for the world to see!
"The two largest planets in our solar system will nearly overlap to form a 'double planet,' an event that hasn’t been easily visible since the Middle Ages—almost 800 years ago. Today’s animated Doodle celebrates the Southern Hemisphere’s first day of summer as well as this rare double planet sighting–-or 'Great Conjunction'–-which can be viewed from anywhere around the globe!
"So what exactly is creating this celestial phenomenon? 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), a once-in-a-lifetime rendezvous recreated in the Doodle artwork. But looks can be deceiving, as the two gas giants will actually remain a vast distance of approximately 450 million miles apart!
"Make sure you look out low above the horizon tonight and take in this momentous meet-and-greet between Jupiter and Saturn–-it’s sure to be out of this world!"
(Source for quote, which includes the actual Doodle: https://www.google.com/doodles/celebrat ... hemisphere)