Those who choose to observe the night sky from July 31 to August 1, witnessed climbing on it blue moon - the term used by astronomers to determine the re-emergence of the full moon in a calendar month. The second is the spectacle will be visible even on the last night of August. If you miss this celestial event, the next time will be able to observe it only has exactly three years - July 31, 2015.
The only satellite of the Earth, however, looks at this period as a regular full moon in any other night. However, the August full moon is considered to be quite rare because it decorates the night sky twice a month, which happens every 2.66 years.
Why? The lunar month lasts about 29.5 days, the time needed for one revolution around the Earth, and during that time the satellite passes through all phases - new moon - full moon - new moon (when the moon is between the Earth and the Sun). We see the moon because of the sunlight that reflects its surface, and to the extent that it revolves around our planet, we see a different side of it lit by the sun. Full moon means that this is a fully-lit sunlight face of the moon.
Usually the full moon appears in the sky only once a month, but because of some terrestrial months 30 or 31 days, in one full moon can be seen twice.
The term blue moon is also used as a synonym of a rare event, but it’s not her real celestial body. In 1883, the eruption of the Indonesian volcano Krakatoa was the cause of the huge amounts of ash emissions high into the atmosphere. Some clouds contained many particles that scatter red light, other colors are allowed to pass through them, according to the information NASA. White rays of the moon, piercing through the clouds of ash, acquired a bluish, and sometimes greenish, as reported on the official website of NASA.
Original: Livescience.com Translation: M. Potter