The term “supermoon” was coined by astrologer Richard Nolle in 1979 as either a new or full Moon that occurs when the Moon is within 90% of perigee, its closest approach to Earth. Since we can’t see new Moons (except when they block the Sun), what has caught the public’s attention in recent decades are full supermoons, as these are the biggest and brightest full Moons of the year.