The Biggest Full Moon of the Year Rises on the Night of the 31st

The Closest Distance Between the Moon and Earth This Year

The Korea Astronomy and Space Science Institute (KASI) announced on the 28th that the largest and roundest full moon (望, Mang) of the year will rise on the evening of the 31st.

Specifically, the largest full moon will appear at 10:36 PM on that day. Earlier this year, the smallest full moon was on February 6th (at 3:29 AM). The size difference between this year’s largest and smallest full moons is about 14%.

The reason the moon appears different in size from Earth is because it orbits Earth in an elliptical path. When the distance between Earth and the moon is closer, the moon appears larger; when farther, it appears smaller. Among full moons, the one rising on August 31st appears the largest because the distance between the moon and Earth is closer compared to other full moon days.

The distance of the full moon rising on the 31st is approximately 357,341 km, which is about 27,000 km closer than the average Earth-moon distance of 384,400 km. The full moon on February 6th was about 405,829 km away, which is more than 21,000 km farther than the average distance.

The moon’s elliptical orbit around Earth causes its distance to vary with a cycle called the anomalistic month (from perigee to perigee), which is about 27.55 days, while the synodic month (from full moon to full moon) is about 29.53 days. Therefore, this phenomenon occurs on a cycle of approximately 14 synodic months.

Although the physical distance between the moon and Earth becomes slightly closer, atmospheric conditions and subjective factors also affect how large the moon appears, so the difference may not be noticeably visible to the naked eye.

On the 31st, the moon will rise at 7:29 PM and set at 7:01 AM the next day, based on Seoul time. Since a full moon rose on the 2nd of this month, this will be the second full moon of August.

For moonrise and moonset times in other regions, please refer to the Korea Astronomy and Space Science Institute’s Astronomy and Space Knowledge Information website under ‘Daily Astronomy - Monthly Sun/Moon Rise and Set Times.’