As Santa Claus makes his annual toy-distribution trip around the world, he will be guided Christmas Eve by Rudolph’s nose — of course — and the light of a brilliant moon. It is the first Christmas full moon we’ve had since 1977, and just the ninth in the course of American history.

The pudgy Christmas moon rises 99 percent illuminated on Dec. 24, serving as all-night lunar lantern for Santa and his reindeer team. On Dec. 25, the moon officially becomes full at 6:11 a.m., just one hour before it sets. The full moon then rises again at 5:32 p.m. on Christmas evening.

There were only three Christmas full moons in all of the 20th century: 1901, 1920 and 1977. For the 19th century, 1806, 1825 and 1863 were years with a Christmas full moon. Enjoy this Christmas full moon, as the next one occurs in 2034. Amazingly, in the 21st century, there will be five altogether, including 2053, 2072 and 2091.

From your grammar school American history classes, you may recall the nation’s first Christmas full moon. It was Dec. 25, 1776, when the full moon may have had historic ramifications. That Christmas moon fell on the night that George Washington and his Continental Army famously crossed the Delaware River from Pennsylvania into New Jersey in pursuit of Hessians fighting for the British.

Needing a battle victory, Washington decided to launch a surprise attack on Trenton, according to the National Museum of the American Revolution. Men, horses and cannons would be ferried across the river to reach Trenton before daybreak. Battling ice, the army crossed the river. Fortunately, dense clouds and a strong winter storm shrouded the bright full moon and hid the army from the Hessian lookouts – otherwise history might be different.

A Christmas full moon occurred in 1863 – a little more than month after Abraham Lincoln delivered his Gettysburg Address. The Harper’s Weekly center illustration by Thomas Nast depicts a furloughed Union soldier returning home for Christmas, plus in another image, a benevolent Santa Claus visits sleeping young children to leave gifts in their bedroom. Interestingly, Nast drew bright beams of light gleaming through the window – presumably from the Christmas full moon.

In 1977, during the most recent Christmas full moon, after loitering for 10 weeks at the top spot atop the Billboard song charts, “You Light Up My Life,” by Debby Boone was displaced by “How Deep is Your Love?” by the Bee Gees. In a note of irony, Debby Boone had toppled the “Star Wars theme/Cantina Band” by Meco. The latest Star Wars movie – “The Force Awakens” – starts Friday.

An earlier version of this story incorrectly said that it’s the first Christmas moon in 27 years. The most recent Christmas moon was in 1977 — 38 years ago.