By MATT MILNER
Courier staff writer
---- — 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.
“The sun has a heartbeat of about 11 years,” Spangler said. “It’s like a human heartbeat. There’s variation to it.”
Such variations in activity have been observed in other sun-like stars. Spangler said it appears to be “a basic property of middle-aged stars.”
Solar weather, which can produce flares and massive explosions called coronal mass ejections, tends to pick up at the peak of the 11-year cycle. But that’s not happening right now. We’re at or near the peak, and there’s just not much going on.
Sunspot activity during the last solar maximum was measured at approximately double the current activity. And the most recent solar minimum was even wimpier.
“The present maximum is low. The previous minimum was really low,” said Spangler.
But something else is happening, too. There appears to be a multi-decadal cycle in the sun’s activity. In 1958, the solar maximum was about three-and-a-half times as busy as it is now. The maximums have declined since.
Why? Spangler said there really isn’t a good answer.
“We don’t know what causes that.”
The lack of activity has led to some speculation that this could mirror the start of the Maunder Minimum, a period of extraordinarily low solar activity. If the 11-year cycle is a mood swing from a middle-aged star, the Maunder Minimum was a full-blown midlife crisis.
The minimum had profound effects on the Earth, where temperatures dropped enough to give the period the nickname, “The Little Ice Age.” But speculation that solar activity could be leading into a similar lull is just that right now: speculation.
Spangler puts little faith in it. Predicting solar activity is tricky. The best models from 2006 predicted an unusually active solar maximum, a prediction we now know was way off the mark.