A supermoon occurs when a full moon coincides with the Moon's closest approach to Earth in its elliptical orbit, known as perigee, making the Moon appear larger and brighter in the sky. This phenomenon results from the Moon's non- circular orbit, which brings it closer to or farther from Earth at different points in its 27-day cycle.
Orbital Mechanics
The Moon orbits Earth in an elliptical path, meaning its distance from Earth varies between approximately 363,300 km (226,000 miles) at perigee and 405,500 km (251,000 miles) at apogee. When a full moon occurs near perigee—specifically within 90% of its closest approach—it is classified as a supermoon. This alignment causes the lunar disk to appear up to 14% larger and 30% brighter than a full moon at apogee, sometimes called a micromoon.
Frequency and Appearance
Supermoons typically occur three to four times a year and often appear in consecutive months due to the alignment of the lunar cycle and orbital position. The term "supermoon" is not an official astronomical designation but a popular term coined by astrologer Richard Nolle in 1979. Despite the dramatic appearance, the size difference is subtle to the naked eye, though the Moon illusion—where the Moon appears larger near the horizon due to visual comparison with terrestrial objects—can enhance the effect.
Tidal and Geophysical Effects
While the Moon's gravitational pull influences ocean tides, the effect during a supermoon is minimal, increasing tidal ranges by only a few centimeters. Claims linking supermoons to natural disasters like earthquakes or volcanic eruptions lack scientific evidence, as such events are no more frequent during supermoons. The primary observable impact is slightly higher spring tides when the Sun, Earth, and Moon align during full or new moons
