Supermoon: When the Moon Appears Largest

A supermoon occurs when a full moon coincides with the moon's closest approach to Earth in its elliptical orbit, known as perigee. During this time, the moon appears up to 14% larger and 30% brighter than when it's at its farthest point (apogee).

The term "supermoon" was coined by astrologer Richard Nolle in 1979, though astronomers prefer the term "perigee full moon" or "perigee syzygy." The phenomenon occurs because the moon's orbit is not perfectly circular but elliptical, with Earth positioned at one focus of the ellipse.

Orbital Mechanics

The moon's orbit around Earth is elliptical, with perigee (closest point) at approximately 356,500 kilometers and apogee (farthest point) at about 406,700 kilometers. This difference of about 50,000 kilometers creates the size variation we observe during supermoons.

Frequency and Timing

Supermoons occur approximately 3-4 times per year, though the exact number varies depending on the definition used. The most dramatic supermoons happen when perigee occurs within hours of the full moon phase, creating the maximum visual impact.

Tidal Forces

Supermoons cause slightly higher tides, known as "spring tides," due to the increased gravitational pull. However, the effect is minimal - typically only a few centimeters higher than normal spring tides.

Seismic Activity

While some studies suggest a correlation between supermoons and increased seismic activity, the scientific consensus is that any effect is extremely small and not practically significant for earthquake prediction.

Throughout history, several supermoons have been particularly noteworthy. The November 14, 2016 supermoon was the closest since January 26, 1948, and won't be surpassed until November 25, 2034. This event was widely photographed and observed worldwide.

The March 19, 2011 supermoon was notable for occurring just days after the devastating earthquake and tsunami in Japan, leading to speculation about lunar influences on seismic activity, though no scientific connection was established.

Best Viewing Times

The best time to observe a supermoon is during moonrise or moonset when the moon appears near the horizon. The "moon illusion" effect makes the moon appear even larger when viewed alongside terrestrial objects like trees or buildings.

Photography Tips

To capture the supermoon's impressive size, use a telephoto lens and include foreground objects for scale. The moon moves quickly across the sky, so faster shutter speeds help avoid motion blur while maintaining sharp details.