OTTUMWA — Is there a name for the inverse of the Blue Moon, a month in which there are two new moons? It’s a good question to be asking because it will happen not just once, but twice in 2014.
Dr. Steven Spangler, an astronomy professor at the University of Iowa, says no. But it is unusual.
“This year, what’s happening is we had a new moon on the first of January, New Year’s Day, and then on January 30,” he said. “Then again on March 1 and March 30. That’s really rare.”
So rare, in fact, that when first asked about it Spangler thought, “this can’t happen at all.”
The lunar calendar and the one we use to mark the year are related, but not precisely. Calendar months have 30 or 31 days most of the time. February is the odd one with 28 or 29 days, depending on the year. The lunar cycle, called the synodic period, takes 29.5 days, so it’s offset just a bit from the monthly calendar.
“Pick any one phase of the moon and the period of time between one phase and the next time is shorter than the calendar month,” Spangler said.
The result is that phases of the moon meander through the year. The first full moon of 2014 was Jan. 16. By the end of the year it will peak earlier in the month, arriving on Dec. 6.
If things line up just right, you wind up with two new moons in a month. The same goes for full moons or any other phase. And since the second new moon of January takes place just before February (the only month that closely matches up with the lunar cycle) begins, the same thing will happen in March.
The multiple months with multiple new moons isn’t the only thing drawing attention. The sun is also much quieter than usual. While the light we notice doesn’t vary all that much, the sun’s activity does.