The next full moon will officially be 100% illuminated at 2:26 p.m. EDT (1826 GMT) on Monday, Aug. 19, 2024. But it won't be just any old full moon, it will be a Supermoon Blue Moon! The exact moonrise time will depend on your location. Sounds pretty cool, but what exactly does that mean? Let's take a look at what makes a "supermoon" and a "Blue Moon" (and what makes a two-in-one Supermoon Blue Moon, of course). The term "supermoon" was first coined by astrologer Richard Nolle in 1979, as "either a new or full moon that occurs when the moon is within 90% of its closest approach to Earth" according to NASA. Full supermoons are the biggest and brightest full moons of the year, appearing approximately 30% brighter and 14% larger than usual. Though this may sound like a lot, it's quite hard to spot the difference with the unaided eye, unless you're a seasoned moon-watcher. However, in some instances, a supermoon (or even a "regular" full moon, for that matter) can appear huge. Most of the time, though, this has nothing to do with astronomy and everything to do with how the human brain works; this is known as a "moon illusion." The moon illusion is a trick of perception where the moon looks much larger near the horizon than it looks high in the sky.