On Halloween, the world viewed a special phenomenon: a global blue moon. Contrary to the name, this moon did not appear blue. “Blue moon” is a term for two full moons in one calendar month. The Farmer’s Almanac shared that October’s previous full moon, called the Harvest Moon, appeared on Oct. 1.

Siobahn Morgan, head of the Department of Earth & Environmental Studies and a professor of astronomy at UNI, said that the event was special due to falling on Halloween in various parts of the world. She estimates that the instance of a blue moon falling on Halloween takes place once every 19 years.

While the blue moon might have made Halloween feel all the spookier, Morgan said that it couldn’t be blamed for any unusual activity. She said that various studies haven’t found evidence to suggest full moons cause unusual activities or increase emergency room visits or police station calls.

Morgan shared that full moons can present problems for astronomers. If they are viewing faint celestial objects, a full moon makes it difficult to see those objects due to its brightness.

Morgan said that a few planets accompanied the blue moon in the sky on Halloween. Mars was visible toward the east and Jupiter toward the south. Saturn appeared faintly near Jupiter. Night sky viewers can identify planets by their brightness and non-twinkling nature.

The full moon was visible anywhere from dusk until dawn, so long as there were no clouds. Morgan said that it rose to the highest in the sky at midnight.

“That’s of course when all the werewolves come out,” Morgan joked.