Jupiter and Saturn will appear to touch in closest conjunction since 1623

We are now just a week away from what astronomers are calling a rare conjunction of the two largest planets in our solar system: Jupiter and Saturn.

Just after sunset on December 21, the two planets -- although still 400 million miles apart -- will appear to touch, illuminating the night sky just days before Christmas.

“The term conjunction refers to anytime you have two celestial bodies which appear close,” said José Cotayo, education specialist at the Museum of Science and Industry in Tampa. “It’s often called the great conjunction when it happens with the two gas giants -- those being Jupiter and Saturn.”

Great conjunctions are not that rare, occurring roughly every two decades based on the aligning orbits of the planets.

However, this year, stargazers should get the best view of it in centuries. Jupiter and Saturn will appear the closest they have since 1623, according to NASA.

The two planets have been drawing closer and closer together in the sky for months.

On Monday, they are expected to appear as a single point of bright light, easily seen in the southwestern sky from anywhere, even with the naked eye.

 Astronomers say binoculars or telescopes will enhance the viewing, making Saturn’s rings and Jupiter’s moons more visible.

Should skies remain clear, "you will be amazed,” Cotayo said.

If you miss the conjunction this time around, Astronomers say it won’t be this close or this visible again until 2080.