The month of August will end with a bright supermoon that will also lead to a rare celestial event - a blue moon when two supermoons occur in the same month). According to American space agency NASA, a supermoon is a perigean moon that occurs near or at the time when the moon is at its closest point in its orbit around earth. The term was coined by an astrologer in 1979. Interestingly, ringed planet Saturn will also make its closest and brightest appearance of the year near the moon.