The Moon is the only natural satellite of the Earth, and the fifth largest satellite in the Solar System. It is the second brightest object in the sky after the Sun.
The Moon makes a complete orbit around the Earth with respect to the fixed stars about once every 27.3 days (its sidereal period). However, since the Earth is moving in its orbit about the Sun at the same time, it takes slightly longer for the Moon to show the same phase to Earth, which is about 29.5 days
1610: Galileo Galilei is the first to use a telescope to make scientific observations of the Moon.
A Blue Moon is commonly the name given to the second full moon in a month. In 1999, there were two blue moons very close together.
- - Jan. 2nd – Jan 31st
- - March 2nd – March 31st
Then we find blue moons in:
- - November 2001,
- - July 2004.
- - May 2007
- - June 2007 for those in Europe and Asia
- - December 2009.
- - August 2012
- - July 2015.
According to wikipedia A blue moon can refer to the third full moon in a season with four full moons.Most years have twelve full moons that occur approximately monthly. In addition to those twelve full lunar cycles, each solar calendar year contains roughly eleven days more than the lunar year of 12 lunations. The extra days accumulate, so every two or three years (7 times in the 19-year Metonic cycle), there is an extra full moon.
In the 19th and early 20th centuries, the Maine Farmers’ Almanac listed blue moon dates for farmers. These correspond to the third full moon in a quarter of the year when there were four full moons (normally a quarter year has three full moons). Full moon names are given to each moon in a season: