By: Michele Berger
Published: August 20,2013
Composite photo of full moon (Flickr/NASA Goddard Space Flight Center)
Hey stargazers, get ready for a blue moon tonight — though it’s likely not the kind you’re thinking of.
First:
No, the moon will not actually be blue. Second: This is not the second
full moon in the month of August, the definition most people probably
think of.
Instead, when Tuesday’s full moon rises to its
peak at 9:45 p.m. eastern time, it’ll be a “seasonal blue moon” — the
third of four full moons in a season. A seasonal blue moon hasn’t
happened in nearly three years, EarthSky reports.
That
we call two different events blue moons is a relatively recent error: In
1980, a radio program used as its source an inaccurate 1946 article
from Sky & Telescope magazine. The
third-full-moon-in-a-season definition is actually correct, but the
modern version is “like a genie that can’t be forced back into its
bottle,” the magazine wrote in 2006.
And while the celestial body itself won’t actually be a sapphire hue this time around, there can actually be a blue-colored moon, according to NASA’s Tony Phillips.
“There was a time, not long ago, when people saw blue moons almost every night.
Full moons, half moons, crescent moons — they were all blue, except
some nights when they were green,” Phillips wrote for NASA’s Solar
System Exploration. “The year was 1883, the year an Indonesian volcano
named Krakatoa exploded.”
The ash, he continued, caused
the unlikely shades, with particles large enough to “strongly scatter
red light, while allowing other colors to pass,” Phillips wrote. “White
moonbeams shining through the clouds emerged blue and sometimes green.”
Krakatoa’s not the only blue-moon causer. It happened after Mount St. Helens erupted in 1980, and again after Mount Pinatubo’s event in the Philippines 11 years later.
Rodgers
and Hart immortalized the blue moon in their 1934 song by the same
name, one that Elvis and Billie Holiday and Mel Tormé all covered. But
it’s a good thing the moons described in songs aren’t all real; if they
were we’d have to look far beyond a cobalt moon to a red one, a black
one, even a chartreuse one. (NASA compiled a list of tunes that describe
the rainbow colors of the moon; the titles clocked in at 19.)
Though blue moons happen more often than “once in a blue moon,” enjoy tonight; the next seasonal one isn’t until May 21, 2016.
MORE: A supermoon! (PHOTOS)
The supermoon sets near the Statue of Liberty, Sunday, June 23, 2013, in New York. (AP Photo/Julio Cortez)
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