First of all, the two planets aren’t going to really collide — that would be a sign to see!
Instead, they are going to appear to touch in our night sky.
Coming up on December 21 is something that hasn’t been seen for hundreds of years, a close conjunction of Jupiter and Saturn. A “conjunction” in astronomy is when two bodies appear at this closest point from our perspective from Earth. Every 20 years, Jupiter and Saturn appear to approach one another. This time, the planets will appear as close as they did back in the 1600s, less than the diameter of a full moon in our night sky.
These two planets have been in our night sky for months, but as we approach December 21, they will be getting closer and closer together. On that night, they will be at their closest point. If we have clear skies, and you have access to a powerful telescope, you will easily be able to see the rings of Saturn and the moons of Jupiter. To see this, you will want to look to the southwest sky right after sunset. The pair will drop below the horizon before 7 p.m. Eastern Time.
So why is this happening? From our perspective in the solar system, Saturn and Jupiter are going to appear lined up. If you were standing on Mars, the view of the night sky would be completely different right now.
Speaking of Mars, it’s high in the southern sky. The constellation Orion is in the eastern sky, and the first quarter moon will be 49.9% illuminated on the night of the conjunction.
Hopefully we will have clear skies, happy viewing!