What some media have called the “Christmas Star” will shine Christmas week in our southwestern sky.

From our perspective here on Earth, two of the brightest objects in the night-sky — Saturn and Jupiter — are moving toward each other and what astronomers call a great conjunction on Monday, Dec. 21, which also happens to be the winter solstice.

Although conjunctions happen every 20 years, when they come together — about a fifth the diameter of a full moon apart — later this month, the two planets will be in the closest conjunction since 1623. They won’t be so extra-close again until March 15, 2080.

They will remain relatively close right through Christmas on Dec. 25, according to EarthSky.org.

NASA notes on its website, “These conjunctions occur every 20 years, and this is an especially close one. Keep in mind that while the two gas giants may appear close, in reality, they are hundreds of millions of miles apart.”

Any apparent meeting of planets in the night-sky is known as a conjunction, but astronomers use the term great conjunction to describe a meeting of the two biggest planets in our solar system.

Jupiter is the brighter of the two, about 12 times brighter than Saturn, which is no slouch and shines as brilliantly as the brightest star.

Look for the two planets shortly after sunset beginning tonight and you will be able to track their nightly progress toward one another. Saturn, which has a golden glow, is just to the east of Jupiter.

Both planets shine steadily rather than twinkling like stars.

Jupiter is the fifth planet from the Sun and takes almost 12 years to complete its orbit. Saturn is the sixth planet out, is the farthest planet we can easily see with the naked eye and makes an orbit of the Sun every 30 years of so.

The difference in their orbits leads to the 20-year cycle for great conjunctions.

“On the evening of closest approach on Dec. 21, they will look like a double planet, separated by only (one-fifth) the diameter of the full moon,” according to EarthSky. “For most telescope viewers, each planet and several of their largest moons will be visible in the same field of view that evening.”

— Marcus Schneck/PennLive/Tribune News Service