July 2015 brings us two full Moons in the same calendar month. But which is a Blue Moon? And why is it called a Blue Moon? There’s been a lot of hype. Get the scoop here.
When is the Blue Moon?
The first full Moon rose on July 1. This was the year’s lowest full moon. At its highest at 1 AM, it didn’t even get one-third of the way up the sky, from typical North American locations. It was much lower than that as seen in Canada or Europe. Low moons look more orange, thanks to the thick air near the horizon. Some have even suggested that its amber color is the origin of the term, “Honey Moon.”
The second full Moon rises on July 31. This second full Moon of the month qualifies as a Blue Moon, according to popular definition.
Why is it Called the Blue Moon?
We got a lot of letters about this. Some folks imagine that it actually appears blue. Others assume it’s a term that originated with Native American folklore. Neither is true.
The inside scoop is that calling any month’s second full Moon a Blue Moon only started in the 1940s as a result of a mistake in an astronomy magazine.But it slowly went viral until nowadays the second full Moon in the same calendar month is widely called a Blue Moon.
The notion has no venerable pedigree among Native Americans, ancient cultures, or anything in the actual sky. So OK, we’ll play along and call it a Blue Moon. Just so you know, it’s a new idea.
Ever heard the expression, “Once in a Blue Moon?” It suggests great rarity. In reality, since the Moon’s period of phases is 29 ½ days, while months usually have 30 or 31 days, it’s obvious that if a full Moon lands on the first day of any month except February it will repeat again at the end.
Turns out, Blue Moons happen every 30 months on average. Two and a half years.
Not so very rare. Once in a Blue Moon? Stick around!
Meantime, enjoy this one, whose color will likely be the exact opposite of blue. Use our sunrise and sunset calculator to find out when you can see the Moon!
Coming soon: The best meteor shower in years!