Friday's rare "blue moon" will coincide with a private funeral service for Neil Armstrong, the first man to walk on the moon.
According to the Associated Press, Armstrong, 82, died last Saturday in Ohio. His family has suggested paying tribute to the astronaut by looking at the moon and giving him a wink.
There is said to be a blue moon — named for its rarity, not its color — when there is a second full moon in one calendar month, reported LiveScience. After Friday's blue moon, one won't be seen again until July 2015. A full moon cycle is 29.5 days, which is why a blue moon is so uncommon.
And a moon that is actually colored blue is even more rare, according to Phys.org. QUT astrophysicist Stephen Hughes said the moon could appear blue, but only if there is smoke or volcanic ash particles suspended in the atmosphere.
More from GlobalPost: Neil Armstrong, first man on the moon, dead at 82
"A blue-tinged moon is a rarity and so maybe that's where the saying came from. There are reports of blue moons after the Krakatoa eruption in Indonesia in 1883 in which volcanic ash was ejected 80km high, on the edge of the ionosphere," he said.
Another rare event is a year with two blue moons, said LiveScience. The last time a single year had two months with two full moons was in 1999. The next time double blue moons will be visible is in 2018.