There will be a full moon in the Chicago area sky this week, but it’s a rare sight that combines two unique events in one night.
According to NASA scientists, the full moon will be a super blue moon and will be the first in a series of “supermoons” in the coming months.
So what makes this moon so interesting and special? Here’s a look.
What is a “supermoon”?
A “supermoon” is a full moon or new moon that occurs when the moon is 90 percent of its closest distance to Earth. Astronomers say the moon’s proximity to Earth results in slightly larger and brighter full moons.
According to NASA, this will mark the first of four consecutive “supermoons,” with the September and October ones both occurring at a time when the moon is even closer to Earth in its orbit.
What is a “blue moon”?
Most Americans know that a “blue moon” is the second full moon in a calendar month, but that definition is actually much newer than the original meaning of the phrase, according to NASA.
According to NASA, the original definition of a “blue moon” was the third full moon in a season that has four full moons in total. There will be a total of four full moons during the astronomical summer, with the last one taking off in September.
Most Americans also know that a “blue moon” is usually not blue in color.
How rare is a “super blue moon”?
Since there are differences in the definition of a supermoon (based on the moon’s proximity to Earth) and a blue moon (whether it’s two full moons in one month or the third full moon in a four-full moon season), it’s difficult to mathematically express how rare a “super blue moon” is.
However, according to USA Today, based on the definitions NASA used for this week’s event, it can be roughly estimated that a “super blue moon” of this type will only occur once every 10 years on average, although the interval could be considerably longer than that.
The gap between “super blue moons” won’t be as big this time around. According to “Full Moon,” there will be seasonal blue moons on May 20, 2027, and December 20, 2029, but the next seasonal “super blue moon” will occur on September 19, 2032.
