Robert Young, amateur astronomer and director of federal programs and testing for Rome City Schools, said that two full moons in December hasn’t happened since 1990. He explained that a “blue moon” is the second full moon that falls within any given month. The moon is not actually blue.
Young explained that a blue moon is commonly explained by the differences in the lunar and monthly calendars. The lunar cycle lasts 29 ½ days, so once every couple of years there will be two moons in a calendar month.
Another blue moon won’t occur again for another two and a half years, and a second full moon in the month of December only occurs three times in a century, Young said.
The next time December sees a second full moon won’t be until 2028.
Click here to visit the U.S. Naval Observatory moon Web site.
“It’s a fascinating and exciting kind of event when you look at it from the standpoint of it being a new year,” he said.
The term “blue moon,” according to Young, was first used as a metaphor of impossibility or absurdity in the 1500s. It wasn’t until the 19th and 20th centuries when a farmer’s almanac began providing explanations of blue moons and when they would occur that the term became popular.
“An interesting thing happened in March 1946 in Sky and Telescope magazine, when James Pruitt wrote an article titled ‘Once in a Blue Moon,’” Young explained. “He took the farmer’s almanac definition and simplified it, and his definition became the second full moon in a calendar month. That is what has stuck.”
Young said full moons during the different months of the year also have names.
For instance, April’s full moon is referred to as a “planter’s moon,” and September’s is known as the “harvest moon.”
“Depending on your culture, all full moons have a name,” he said.
“Any time you can get excited about astronomy or stargazing, it’s a good thing,” Young said. “It’s also nice that there are two romantic evenings in a month.”