As one can easily deduct from the popular saying, "once in a blue moon," blue moons are rare; but the blue moon that's expected to hang in the night sky on Fri., Aug. 31 will be particularly noteworthy.
Friday's blue moon is the last blue moon that will be seen until 2015.
Blue moons, according to LifeScience, are defined as the second full moon in a month or the fourth full moon in a season.
Friday's full moon will be the second of the month, with .