The Christmas night sky 2023: The Northern Cross lights the way

The Yuletide evening sky is especially rewarding now. The eastern sky is filled with brilliant stars — sort of a celestial Christmas tree. Distinctive groupings of stars forming part of the recognized constellation outlines, or lying within their boundaries, are known as asterisms. Ranging in size from sprawling naked eye figures to minute stellar settings, they are found in every quarter of the sky and at all seasons of the year.  

The larger asterisms — ones like the Big Dipper in Ursa Major and the Great Square of Pegasus — are often better known than their host constellations. One of the most famous is in the northwest these frosty evenings. 

Originally known simply as the "Bird" in ancient times, without any indication of what sort of bird it was supposed to represent, it later became the constellation Cygnus, the Swan. But the brightest six stars of Cygnus compose an asterism more popularly called the Northern Cross. Bright Deneb decorates the top of the Cross. Albereo, at the foot of the Cross, is really a pair of stars of beautifully contrasting colors: A third magnitude orange star and its fifth magnitude blue companion are clearly visible in even a low power telescope.

While usually regarded as a summertime pattern, the Cross is best oriented for viewing now, appearing to stand majestically upright on the northwest horizon at around 8:30 p.m. local time, forming an appropriate Christmas symbol. Furthermore, just before dawn on Easter morning the cross lies on its side in the eastern sky.

Related: Night sky, December 2023: What you can see tonight

Joe Rao

Joe Rao is a veteran meteorologist and eclipse chaser who also serves as an instructor and guest lecturer at New York's Hayden Planetarium. 

The Christmas Package

Look over toward the southeast part of the sky at around the same time. Can you see a large package in the sky, tied with a pretty bow across the middle? Four bright stars outline the package, while three close together and in a straight line make up the decorative bow. 

Now you can see how our modern imagination might work, but tradition tells us that those seven stars formed a mighty hunter called Orion, the most brilliant of the constellations and visible from every inhabited part of the Earth. Two stars mark his shoulders, two more his knees and three his belt.

As is also the case with the mighty Hercules, the figure of Orion has been associated in virtually all-ancient cultures with great national heroes, warriors, or demigods. Yet, in contrast to Hercules, who was credited with a detailed series of exploits, Orion seems to us a vague and shadowy figure. The ancient mythological stories of Orion are so many and so confused that it is almost impossible to choose among all of them. 

Even the origin of the name Orion is obscure, though some scholars have suggested a connection with the Greek "Arion," meaning simply warrior. All, however, agree that he was the mightiest hunter in the world and he is always pictured in the stars with his club upraised in his right hand. Hanging from his upraised left hand is the skin of a great lion he has killed and which he is brandishing in the face of Taurus, the Bull, who is charging down upon him. 

The Heavenly Manger

The legendary French astronomer Nicolas Camille Flammarion (1842-1925) referred to the three belt stars of Orion as "The Three Kings." And if we were to consider these three stars as representing the Magi, then not too far away, to the east, within the faint zodiacal constellation of Cancer, is the star cluster known as Preasepe, the Manger. 

A manger is defined as a trough or open box in which feed for horses or cattle is placed. But the Book of St. Luke also tells us that the baby Jesus, wrapped in swaddling clothes was set down in a manger because there was no room at the Inn. In our current Christmas week evening sky, Preasepe represents the manger where Christ was born. 

In the sky, the constellation of Cancer is practically an empty space in the sky, positioned between the Twin Stars (Pollux and Castor) of Gemini and the Sickle of Leo. It's completely devoid of any bright stars and would probably not even be considered a constellation at all were it not for the fact that there had to be a sign of the Zodiac between Gemini and Leo. 

In the middle of Cancer are two stars called the Aselli ("donkeys") that are feeding from the manger; Asselus Borealis and Asselus Australis bracket Preasepe to the north and south, respectively. To the unaided eye the manger appears as a soft, fuzzy patch or dim glow. But in good binoculars and low-power telescopes, it is a beautiful object to behold, appearing to contain a splattering of several dozen stars. Using his crude telescope, Galileo wrote in 1610 of seeing Preasepe not as one fuzzy star, but as ". . . a mass of more than 40 small stars." 

Not quite a Christmas full moon in 2023

If you've ever received a Christmas card with Santa Claus and his reindeer flying across the nighttime sky, there's a pretty good chance that along with a scattering of stars you're also going to have a full moon as well. A full moon coinciding with Christmas is a tradition which can be traced back to the poem "A Visit from St. Nicholas" first published in 1823. We can recall the moment when Saint Nick was about to make his first appearance; the narrator described his view through his bedroom window: 

"The moon on the breast of the new fallen snow, Gave the luster of mid-day to objects below."

This year, it might appear at first glance that a full moon adorns our Christmas night sky, but that will not be the case. The moon will not officially turn full until 7:33 p.m. Eastern Time on the night after Christmas (Dec. 26) when the Full Cold Moon rises. On Christmas night, the moon will still be a waxing gibbous phase, 99-percent illuminated; on Christmas Eve it will shine 96-percent of full. 

In fact, for many, the moon might be two or even three days before full, or two or three days after full, but still, many will likely remark: "Hey!  Look at the full moon!"  Most people, at least at first glance, can't seem to tell the difference between a 100-percent illuminated moon versus a 90-percent illuminated moon. 

For the record, the next time a full moon coincides with Christmas Night will be in 2034.

The Shepherd's Star

If you are up about an hour or so before sunrise, look toward the east-southeast to get a glimpse of what Flammarion described as "The Shepherd's Star," the planet Venus. He wrote: 

"She shines in the east in the morning, with a splendid brightness which eclipses that of all the stars. She is, without comparison, the most magnificent star of our sky; the star of sweet confidences."

Indeed, Venus is always bright and this year it will remind those who arise early on Christmas morning of the Biblical "Star in the East." 

Telescope Targets

Lastly, for those who receive a telescope for a holiday gift, while Venus will be rather disappointing, appearing as a less-than-appealing gibbous phase, there are two other splendid planetary targets to gaze at. That very bright "star" that you notice at day's end in December, glowing about halfway up from the east-northeast horizon right after sundown is Jupiter; a superb telescopic showpiece with cloud bands crossing its disk, as well as its retinue of four large moons.

And lastly, also in the evening sky is "the lord of the rings," Saturn, which this week can be found at dusk well up in the south-southwest sky. A telescope magnifying 30 power or more will reveal Saturn's famous rings, now tilted about 9 degrees to our line of sight.

Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for Natural History magazine, the Farmers' Almanac and other publications.