First humans to circle a celestial extraterrestrial body (Apollo 8, Dec. 24 - 25, 1968)

from Writer's Almanac (American Public Media, Garrison Keillor):
In 1968, the Apollo 8 spacecraft entered orbit around the moon on Christmas Eve - Day. Frank Borman, Jim Lovell, and William Anders became the first humans to orbit a celestial body other than our Earth. Apollo 8 circled the moon 10 times over the next 20 hours, while the astronauts tested equipment and took many photographs of the moon’s surface. It was the first manned space mission to the moon, and it was a crucial step toward meeting the Apollo mission’s ultimate goal — putting a man on the surface of the moon. NASA would achieve that goal less than a year later.
The astronauts sent a Christmas Eve broadcast home to Earth from their path around the moon. Borman later recalled, “We were told that on Christmas Eve we would have the largest audience that had ever listened to a human voice, and the only instructions that we got from NASA was to do something appropriate.” All three astronauts took turns reading from the Book of Genesis, which begins, “In the beginning God created the heaven and the earth. And the earth was without form, and void; and darkness was upon the face of the deep. And the Spirit of God moved upon the face of the waters. And God said, Let there be light: and there was light. And God saw the light, that it was good: and God divided the light from the darkness.”
William Anders later said that although the astronauts went on their mission to explore the moon, what they really discovered was the planet Earth. He added: “I think it’s important for people to understand they are just going around on one of the smaller grains of sand on one of the spiral arms of this kind of puny galaxy [...] it [Earth] is insignificant, but it’s the only one we’ve got.”