‘Once in a blue moon’ coming up Friday

Every few years, two full moons fall in the same calendar month. This is known to astronomers as a “blue moon.”

This “second full moon in one month”, will not occur again until July 2015.

We get two full Moons in a month — sometimes — because, in part, it takes the Moon approximately 27 days, 7 hours, and 43.2 minutes to go around the Earth once. This is called a sidereal month. However, the Earth is also going around the Sun. So during these 27-plus days, the Earth has progressed a little ways around the Sun.

The synodic month is the period in which the Moon takes to line up with the Sun and the Earth exactly as it did at the beginning of that period. That amount of time is about 29.5 days, or the synodic month.

The average month has 30 days, so there is a slight chance that a full Moon will occur at the beginning of the month and then again, at the end of the month. And, this is happening in August of 2012. On average, about 27 Blue Moons occur in any given century. So far, in the twenty-first century, we’ve had five of them.

In any case, go outside and watch the Moon be Full and be a Blue Moon on Friday, August 31, 2012. Hopefully you’ll have a clear night sky over your locality on Earth.
(Courtesy: www.itwire.com)