Later this month there will be a 'blue moon'

Astronomers are about to see the first "blue moon" in nearly two years, the second full moon in a month.

"Blue Moon" will appear later this month

According to UPI, this July will have two full moon, the first on July 2, and the second will appear on the last day of July 31.

Blue moon will appear at the end of July. (Artwork: Moms Clean Airforce)

"Blue moon" is an English term used to refer to the phenomenon of the full moon twice a month, which does not mean the moon emits blue light. Some documents noted that the moon was blue in 1980 and 1991 due to air pollution (dust particles dispersed blue light, making the moon green).

The last time the " blue moon " appeared at the end of August 2012.

"Blue moon " exists because the month in the Calendar does not coincide with the month in the moon cycle, usually every year there are 12 full moon periods corresponding to 12 months, but because the moon revolves around the earth for 29.5 days; In the solar calendar months there are 30 or 31 days so each calendar year has more than 11 days compared to the lunar year, so after about 2-3 years there will be a lunar year with 13 months, corresponding to 13 times full moon.