DHAKA: In a delight for skywatchers, the second full moon of July made its appearance on Friday evening. The rare phenomenon - the sighting of second full moon - is referred to as Blue Moon.

The first full moon of the month had appeared on July 2. Usually, in a calendar year, only one full moon is visible every month.

In addition to those 12 full lunar cycles, each calendar year contains an excess of roughly 11 days due to the difference between lunar and solar years. These extra days accumulate, and every two or three years, there is an extra full moon.

The "blue moon" name is used when an extra full moon appears within a specific time period, like a month or season.

The last time the event occurred in August 2012. The next time it will occur in January 2018.

The moon is known to turn a distinctly blue colour when smoke or dust particles hang in the air, usually caused by wildfires or a volcano eruption.

In 1883, the moon turned blue for weeks after the volcano Krakatoa exploded with the force of a nuclear bomb between Sumatra and Java.

Source: Sky News, NDTV
BDST: 1052 HRS, AUG 1, 2015
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