Blue Moon in May 2007
May 31, 2007, Holds the Second Full Moon of the Month
On May 31, 2007, a Blue Moon will occur. The simple definition of a Blue Moon is a second full moon occurring within one calendar month.
A Full Moon occurs once every 29 and a half days as the Moon orbits Earth. When the Moon is positioned on the opposite side of Earth from the Sun, Earthly inhabitants see the completely lit side of the Moon. Because this happens once every 29 and a half days and because a calendar month can be up to 31 days long, there are occasions when a Full Moon occurs on one of the first couple days of the month and is then in position to occur again on one of the last days of that month. This is what happens in May of 2007.
On May 2, 2007, a Full Moon occurred at 6:09 a.m. EDT. On May 31, 2007, a Full Moon will occur at 9:04 p.m. EDT. Look for a magnificent Full Moon rising over the Eastern horizon as the sun sets.
But will the moon appear blue? No. Our human tinkering with dates and calendars has no effect on the Moon.
So how did the term Blue Moon come about? The magazine Sky and Telescope has traced the use of Blue Moon back to themselves, when they mistakenly identified a Blue Moon as the second Full Moon in a month. Historically, a Blue Moon was referred to by the Farmer's Almanac as the third Full Moon in a season that has four Full Moons. But it has no actual bearing on the color of the Moon.
How often is "Once in a Blue Moon" ? Blue Moons occur approximately once every two and a half years, which would make it a relative rarity when compared to regular Full Moons.
Does the Moon ever change color? Yes, sort of. It doesn't physically change color itself, but it appears to take on different colors depending on what is in the atmosphere of Earth. Lunar eclipses can cause the moon to look red, orange, or even black, and smoke and dust in the atmosphere from wildfires and volcanic eruptions can also change the color of the Moon's appearance, including making it look bluer on occasion.
On May 31, look for the bright and reddish star Antares leading the Moon across the sky and find Jupiter as the bright yellowish-white "star" next to the Moon.
So turn on the song Blue Moon by Frank Sinatra (or Elvis or Ella Fitzgerald if you wish) and gaze at the Blue Moon in May. And don't be surprised if it doesn't look blue. For as the lyrics say, "And when I looked the Moon had turned to gold."
Check here for other observing highlights for May 2007.
Or check out observing highlights for June 2007.
