Is the 2007 blue moon on May 31?
Full moon setting at dawn over Chisos Mountains in Big Bend National Park, courtesy NPS.
Thursday, May 31, 2007.
There’s a full moon every month, and every full moon has a special name.
When there’s a second full moon of a calendar month, it’s come to be called a Blue Moon. But whether you call tonight’s full moon a Blue Moon – or give that name to the full moon at the end of next month – will depend on where you live on the globe. The full moon reaches the crest of its full phase on June 1st, at 1:04 a.m. Universal Time. That’s a time used by astronomers: a single time for the whole globe of the Earth.
But for the rest of us, Earth is divided into about 24 separate time zones. So, although the moon will reach the crest of its full phase on June 1st for some parts of Earth, that same fullest moment of full moon might come tonight for you. This full moon will come before dawn tomorrow for Europe. Likewise, for Africa, Asia, Australia, and New Zealand, the moon is full on June 1st.
But if you’re in the U.S., the full moon comes before midnight tonight… and that makes tonight’s moon the Blue Moon. No matter where you live, a full–looking moon will shine all night tonight. And the name Blue Moon is just a name, after all. According to modern folklore, it’s the name for the second full moon of a calendar month and has nothing to do with the moon’s color.
Look for a very bright object near the moon tonight – the planet Jupiter.
Origin of modern–day definition of Blue Moon
Dates and times of the Full Moons – Farmers’ Almanac
Moon Phases by the US Naval Observatory
Every year, on or near today’s date, the sun is in conjunction with Aldebaran, the brightest star in the constellation Taurus the Bull. What’s more – the star Antares, the heart of the constellation Scorpius the Scorpion, always stands opposite of Aldebaran in our sky. Because the moon – when full – is opposite of the sun, that means the moon and Antares will be close together throughout the night. In fact, if you were at the right place on Earth, you’d see the moon occulting – passing right in front of – Antares, eclipsing the heart of the Scorpion for an hour or so tonight.
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Actually, not to pick nits, but the editor of Sky and Telescope was on NPR last night claiming that they mistakenly called the second full moon in the same calendar month a “blue moon,” even though its normal use—before the error was widely propogated in 1948 or so—was to indicate the fourth moon in a season. If I understand correctly, this means that there’s at least one blue moon a year, as there are 13 full moons (I think—am I right) in a year, and only 12 months. Thus, a 2nd full moon in a month would still be a blue moon under the more “acceptable” definition.
Does this make sense? Thanks.
I love your site. Keep up the good work and enjoy the sky.
I am reveling my beautiful blue moon!
Hi Tom, here’s an article about how the term “blue moon” entered the popular culture, with the current meaning of “the second full moon of a single month.” It’s by folklorist Phillip Hiscock, and it’s called Folkore of the Blue Moon.
I’m very familiar with this article, because both Sky & Telescope and my original radio series Star Date played a role.
I personally think Sky & Telescope makes too much of this “error” from their original 1940s article. The blue moon phenomenon has been a fascinating thing to watch … folklore in the making!
All the best,
Deborah
Joe … thank you!
Ladybug … me too!
Best to all,
Deborah
Hi Tom.
Yes, you are correct. Apparently, the popular definition of blue moon – the second of two full moons to occur in the same calendar month – originated from a misinterpretation of the Maine Farmer’s Almanac blue moon definition: the third of four full moons in one season. This Sky & Telescope article elaborates.
More often than not, there are 12 (not 13) full moons in one calendar year. If there are 13 full moons in one calendar year, then it’s inevitable: there has to be at least one calendar month with two full moons. If there is no full moon in February (like in 1999 and 2018), then there are two calendar months with two full moons.
Bruce McClure
Dear Earth and Sky,
You can’t have it both ways. You state in your article that tonight’s moon is the “blue moon” going with the concept that it is the second moon in May but you also state that the official full moon doesn’t happen until June 1.
Then you state that if we think tonight’s moon is in June then the moon on June 30 will be the “blue moon” because it is the second moon in June. But, you reference an article that mentions that the original definition of a “blue moon” is the 3rd moon of the 4 moons during a season.
Using this definition, then tonight’s moon is the “blue moon” no matter which month it falls into.
Hi, again,
I am with Deborah on this—I think the folklore aspects are most interesting, and, in the end, there’s no “technical” astronomical term for this phenomenon. Alas, it’s cloudy here in upstate NY right now, so we may not see this blue moon, but any full moon is a reason to look up and celebrate—at least, my 5 and 3 year olds think so!
Bob,
For international usage, astronomical almanacs give the times of astronomical events in Universal Time. Universal Time represents the standard time zone at the Earth’s prime meridian (0 degrees longitude), which passes through Greenwich, England. Oftentimes, lunar phases, equinoxes, solstices, eclipses and other astronomical events happen on different dates, depending upon your position on the globe.
In Greenwich, England, tonight’s moon is full at precisely 1:04 a.m. standard time (2:04 a.m. daylight savings time) on JUNE 1. For the Central Time Zone in the United States, you have to subtract 5 hours to convert Universal Time to Central Daylight Time. That places tonight’s full moon at 8:04 p.m. CDT on MAY 31. For a fuller explanation, I recommend this web site.
No, tonight’s full moon is NOT a blue moon by the older definition of the term (the third of four full moons in one season). All the seasons this year have three and only three full moons.
Next year – in 2008 – there will be 4 full moons between the March equinox and the June solstice. In England, the third of these four full moons will fall on May 20, 2008; and in the United States, this same full moon will fall on May 19, 2008.
Bruce McClure
Along with Tom and Deborah, I also celebrate the blue moon phenomenon – folklore in the making!
To state it as simply as I know how: if there are 13 full moons in ONE CALENDAR YEAR, then you have at least one calendar month with two full moons; on the other hand, if you have 13 full moons between SUCCESSIVE DECEMBER SOLSTICES, then one of the four seasons has to have 4 full moons.
In a nutshell, that was the source of the confusion.
Bruce