The next full moon, occurring on Monday, Aug. 19 at 1:26 p.m., isn’t just any old full moon —it’s a Supermoon Blue Moon.
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, however, 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.
This illusion occurs because of how our brain interprets distance and size. When the moon is near the horizon, we see it alongside trees, buildings and other objects. That gives us a sense of scale, so our brain compares the moon to these nearby objects, making it appear larger. When the moon is higher up in the sky, there’s nothing to compare it to, so it looks smaller. Photographers sometimes use this effect to capture stunning images of distant objects with the moon appearing extremely large behind them.
August’s full Moon will appear on the afternoon of Monday, August 19, reaching peak illumination at 1:26 P.M. Eastern Time. That evening, look toward the southeast after sunset to catch a glimpse of the Sturgeon Moon rising.
August’s supermoon will be the first of four this year, with the others occurring on Sept. 17, Oct. 17 and Nov. 15. The closest supermoon will be October’s Hunter’s Moon, rising at 7:26 a.m. ET (1126 GMT) on Oct. 17.
