This is last big event of the year. The planets Jupiter and Saturn, known as the Gas Giants, have been close in the sky for most of this year. But on the evening of December 21 they will appear closer together in the sky than at any time since 1623!
If the weather is clear, about 45 minutes after sunset, look 10º above the south-southwest horizon to see Jupiter and Saturn shining almost as one and the brightest objects in the night sky - you may need binoculars to try to see them as separate objects.
They will be close for the week before and after, but 21st is the day.
Great Conjunctions, named because it involves the largest planets in the Solar System, only happen every 20 years and most are not as close as this years. If the weather is bad I am sorry to tell you the next close Great Conjunction is 60 years away!
If you use even moderate binoculars you will see the four satellites of Jupiter and that the planet has a round disk, it is not a point of light like a star. Saturn need a little more magnification than most binoculars can achieve but you can still plainly see it is not a star, and you will see several of its satellites.
But don’t wait until the 21st, Jupiter and Saturn can be seen low in the south west after sunset all December. The thin crescent Moon will be just below them on the 17th.