A supermoon is a full Moon that appears unusually large and bright because it coincides with the Moon being at or near its closest point to Earth in its elliptical orbit, a moment called perigee. Key points

• Perigee and full Moon: A supermoon happens when the Moon is both full and near perigee during that phase. This alignment makes the Moon appear larger and more luminous than a typical full Moon.

• Orbital geometry: The Moon’s orbit around Earth is not a perfect circle; its distance varies roughly between about 360,000 km (at farthest points) and about 400,000 km (at closest points) over its ~27-day cycle. The combination of full illumination and reduced Earth–Moon distance causes the enhanced size and brightness.

• How often: Supermoons occur several times a year, though the exact number and timing vary because the Moon’s orbital plane and distance change relative to the Sun–Earth geometry. They are not guaranteed every month, and distances at perigee differ from event to event.

• Terminology note: “Supermoon” is not an official astronomical term, but it’s a widely used popular descriptor for this coincident full Moon-at-perigee event.

Quick takeaway

• Visual effect: The Moon looks noticeably larger near the horizon and brighter in the night sky when a supermoon occurs, due to its proximity at perigee combined with full illumination.

If you’d like, I can pull a few sources with the latest explanations and any upcoming supermoon dates for your location.