Astronomy Minute: December 2020

By Russ Hanson

Finally, on December 21st, we’ll get to witness a once-in-twenty-years event – if the sky is clear. Yes, the great conjunction will occur on the December solstice. It takes Jupiter, with its shorter and faster orbit, 20 years to overtake Saturn. On December 21st, these two planets will be as close to each other in our sky as they ever get.

Unfortunately, Jupiter won’t occult Saturn. That’s because the orbits of the planets don’t line up perfectly with the plane of the solar system. If you’ve been watching these two planets over the last few months, you will have observed that they are not only getting closer to each other, but they are also moving westward across the night sky.

So make sure you look to the southwest as soon as it gets dark so you don’t miss it. They’ll do it again in 2040, but won’t be as close to each other.