🔭 Events Tools

Special Lunar Events

Beyond the regular monthly cycle of phases, the Moon produces several notable astronomical events that attract widespread interest from astronomers, photographers, and the general public. These events — supermoons, blue moons, and lunar eclipses — all arise from the geometry of the Earth-Moon-Sun system combined with the Moon's elliptical orbit.

What is a Supermoon?

A supermoon occurs when a full moon (or new moon) coincides closely with perigee — the point in the Moon's elliptical orbit where it is nearest to Earth. At perigee, the Moon is approximately 356,500 km away; at apogee it is about 406,700 km away. A perigee full moon appears roughly 14% larger in diameter and about 30% brighter than an apogee full moon. The term "supermoon" is not a formal astronomical term — it was coined by astrologer Richard Nolle in 1979 — but it has become widely used in popular culture. There is typically 3–4 supermoons per year.

What is a Blue Moon?

The popular modern definition of a blue moon is the second full moon in a single calendar month. Because the lunar cycle is 29.53 days and most months have 30–31 days, a second full moon in one month occurs roughly every 2.5 years — hence the phrase "once in a blue moon." An older folkloric definition defines a blue moon as the third full moon in a season that contains four full moons (most seasons have three). The Moon very rarely actually appears blue; this can happen when smoke or dust particles of a specific size scatter red light, such as after major wildfires or volcanic eruptions.

Lunar Eclipses

A lunar eclipse occurs when Earth passes directly between the Sun and the Moon, casting its shadow on the lunar surface. This can only happen at full moon. There are three types: a total lunar eclipse (the Moon passes fully into Earth's dark umbral shadow, turning a deep red or orange from sunlight refracted through Earth's atmosphere — giving the dramatic "blood moon" appearance); a partial lunar eclipse (only part of the Moon enters the umbra); and a penumbral lunar eclipse (the Moon passes through Earth's lighter outer shadow, causing a subtle darkening). Lunar eclipses occur approximately 2–4 times per year, but are only visible from the half of Earth where the Moon is above the horizon at that time.

Next Full Moon and New Moon Tracking

Knowing the date of the next full moon is useful for planning photography outings, outdoor activities, and observing the sky. Full moons occur every 29.53 days; the exact date shifts slightly each month due to the fractional part of the synodic period. New moons mark the start of the lunar month in many calendars, and are the best time for stargazing because the sky is darkest without moonlight.