Hey Ray: Christmas Star To Shine Brightly In The Evening Sky

PITTSBURGH (KDKA) -- When you look at the universe, and all of its moving parts, it looks like a bunch of chaos. However, when you shrink the scope of your view from the universe, to the galaxy, or even the solar system, that chaos becomes a little more manageable, and you can start to see some order from Earth.

One of the events that shows up from time to time, if you pay attention the order is the "Great Conjunction" of Jupiter and Saturn. The two gas giants will appear so close to each other in the sky, that they will look like one, brilliant star. Some are even calling this the "Christmas Star" because the two planets will appear closest to each other on the Winter Solstice, December 21st, days before Christmas. While this happens about every 20 years, the two planets don't usually get this close, and sometimes the sun can be a spoiler. This year, that is not the case. We are looking at the best and closest view of the "Great Conjunction" since the year 1226!

So why is this such a rare event?

Mike Hennessy from the Buhl Planetarium at the Carnegie Science Center says, "I like to think of them as runners on a track. You have the sun at the center of the track and the Earth traveling really fast around the inside track."

One trip around the track is one year for Earth. That is because the "tracks" in these analogies are orbits around the sun.

Hennessy goes on to say, "Jupiter is taking a lap every twelve years around the sun. Saturn is going much slower and is twice as far out, and it's on a much bigger track going around the Sun every 29 years. So, the mechanics have to deal with our perspective looking up at these other two runners. Once every 20 years, from our perspective, we look up and see Jupiter and Saturn tagging up".