Understanding the Moon's Orbit
To understand a supermoon, we first need to understand the Moon's orbit. The Moon does not circle the Earth in a perfect circle; its path is an ellipse, like a slightly squashed circle. This means that its distance from Earth varies throughout its orbit. The point in the orbit where the Moon is closest to Earth is called **perigee**. The point where it is farthest away is called **apogee**. A supermoon is simply a full moon that occurs when the Moon is at or very near its perigee. The technical term for this event is a "perigee-syzygy," but "supermoon," a term coined by an astrologer in 1979, has become far more popular.
How "Super" is a Supermoon?
When a supermoon occurs, the Moon can appear up to **14% larger** in diameter and **30% brighter** than a full moon at its apogee (sometimes called a "micromoon"). While this is a significant difference, it can be difficult for a casual observer to notice without a direct comparison. The change in apparent size is roughly the same as the difference between a U.S. quarter and a U.S. nickel. The most noticeable effect for many people is the increased brightness, which can cast surprisingly strong shadows on a clear night. You can track the dates of all full moons, including supermoons, on our Moon Phase Calendar.
Observing a Supermoon: Tips for the Best View
The best time to observe a supermoon is during "moonrise," just as the Moon is appearing above the horizon. At this time, an optical illusion known as the "Moon Illusion" makes the Moon appear massive compared to trees, buildings, and other objects in the foreground. This effect, combined with the actual increased size of the supermoon, can create a truly breathtaking and memorable view.
- Find an Unobstructed View: Look for a spot with a clear view of the eastern horizon to catch the moonrise.
- Know the Moonrise Time: The Moon rises at a different time each day. Check a tool like our Sunrise & Sunset Calculator to find the exact moonrise time for your location.
- Use Binoculars or a Telescope: While visible with the naked eye, using binoculars will reveal stunning surface details like craters and maria (the dark plains) made more brilliant by the extra brightness.
Do Supermoons Cause Natural Disasters?
A common myth is that supermoons can trigger earthquakes or volcanic eruptions. There is no scientific evidence to support this claim. The Moon's gravitational pull does affect the Earth's tides, and at perigee, this effect is slightly stronger. This can lead to slightly higher tides, known as "perigean spring tides," but the effect is minor and well within the normal tidal range. The Moon's gravitational influence on the Earth's crust is far too small to trigger major geological events.
Conclusion: A Celestial Spectacle
A supermoon is a wonderful opportunity to connect with the cosmos. It's a reminder of the dynamic, ever-changing dance between the Earth and the Moon. While the term may have originated in astrology, the event itself is a beautiful and natural astronomical phenomenon that encourages us all to look up and appreciate the beauty of our nearest celestial neighbor. Don't miss the next one!