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What Is a Supermoon and When Is the Next One?

A Supermoon happens when a Full Moon or New Moon coincides with the Moon's closest approach to Earth; also called perigee.

Full Moon over Denver, Colorado, US.

A Supermoon can be a Full or New Moon.

A Super Full Moon is visible to us, but a Super New Moon is not.

©bigstockphoto.com/ duallogic

A Super Full Moon looks around 12% to 14% bigger than its counterpart, the Micromoon.

Next Supermoon December 2017

The next Supermoon will be on December 3, 2017.

The Supermoon on November 14, 2016, was the closest since January 26, 1948. The next time a Full Moon will come even closer to Earth is on November 25, 2034 (dates based on UTC time).

Perigee and Apogee

The Moon's orbit around Earth is not a perfect circle, but elliptical, with one side closer to Earth than the other.

As a result of the Moon's elliptical orbit, the distance between the Moon and Earth varies throughout the month and the year. On average the distance is about 382,900 kilometers (238,000 miles).

The point on the Moon's orbit closest to Earth is called the perigee and the point farthest away is the apogee.

Super Full Moon and Super New Moon

Illustrative comparison of a Supermoon and Micromoon.
A Super Full Moon looks larger.
According to NASA, a Super Full Moon looks around 12% to 14% bigger than a Micromoon.

When a Full Moon coincides with its closest approach to Earth, it is called a Super Full Moon. A New Moon that takes place when the Moon is around its perigee is known as a Super New Moon.

A Micromoon, on the other hand, is when a Full or a New Moon is farthest from the Earth, around apogee. It's also known as a Minimoon, Mini Full Moon, or a Mini New Moon.

Not an Official Name

Supermoon is not an official astronomical term. It was first coined by an astrologer, Richard Nolle, in 1979. He defined it as ‘a New or a Full Moon that occurs when the Moon is at or near (within 90% of) its closest approach to Earth in its orbit’. It is not clear why he chose the 90% cut off in his definition.

There are no official rules as to how close or far the Moon must be to qualify as a Supermoon or a Micro Moon. Different outlets use different definitions. Due to this, a Full Moon classified as a Supermoon by one source may not qualify as a Super Full Moon by another.

Supermoon Definition

The following definitions are used at timeanddate.com:

  • Supermoon: A Full or New Moon that occurs when the center of the Moon is less than 360,000 kilometers (ca. 223,694 miles) from the center of Earth.
  • Micromoon: A Full Moon or New Moon that takes place when the center of the Moon is farther than 405,000 kilometers (ca. 251,655 miles) from the center of Earth.

Technical Name: Perigee-syzygy

The technical term for a Supermoon is perigee-syzygy of the Earth-Moon-Sun system. In astronomy, the term syzygy refers to the straight-line configuration of three celestial bodies.

When the Moon is close to the lunar nodes of its path during syzygy, it causes a total solar eclipse or a total lunar eclipse

Looks Bigger and Brighter

The Full Moon setting over Jobs Peak, Carson Valley, Nevada.
The Full Moon looks larger near the horizon.
A Full Moon near the horizon looks bigger and brighter than when the same Full Moon is higher in the Sky.
©iStockphoto.com/Jason Woodcock

Because it's so close to Earth, a Super Full Moon looks about 7% bigger than an average Full Moon. When compared to a Micromoon, it looks about 12% to 14% larger.

A Super Full Moon also looks about 30% brighter than a Micro Full Moon and about 16% brighter than an average Full Moon.

Biggest During Winter

Supermoons during Northern Hemisphere winter months tend to look larger than Supermoons that occur during the rest of the year. At this time of the year, Earth is closer to the Sun. Because of this, the Sun's gravity pulls the Moon closer to Earth, making any winter Super Full Moons look bigger than summer Super Full Moons.

Best at Moonrise

The best time to enjoy a Super Full Moon is after moonrise when the Moon is just above the horizon, weather permitting. At this position, a Super Full Moon will look bigger and brighter than when it's higher up in the sky because you can compare the apparent size of the Moon with elements in the landscape like hills, foliage, and buildings. This effect is called the Moon Illusion.

Tidal Effects

The Full Moon lighting up the ocean.
The Moon's gravitational pull causes tides.
The Moon's gravitational pull causes tides.
©bigstockphoto.com/duallogic

The tides on Earth are mostly generated by the Moon’s gravitational pull, in combination with the Sun. The tidal range, which is the difference between high and low tide, is greatest at Full and New Moon because the Sun and Moon are aligned on the same or opposite sides of Earth, and the oceans are affected by the combined gravitational pull of both the Sun and the Moon.

During Supermoons, the gravitational pull leads to even larger variation between high and low tides. It causes higher spring tides, known as perigean spring tides. This has nothing to do with the season spring, but rather it is a synonym for jump or leap.

The tidal range is smallest during the 2 Quarter Moons (Half Moons). These tides are known as neaps or neap tide, from Anglo-Saxon, meaning without the power.

Natural Disaster Trigger?

Although the Sun and the Moon’s alignment cause a small increase in tectonic activity, the effects of the Supermoon on Earth are minor. Many scientists have conducted studies, and they haven’t found anything significant that can link the Super Moon to natural disasters.

According to NASA, the combination of the Moon being at its closest and at Full Moon, should not affect the internal energy balance of the Earth since there are lunar tides every day.

Topics: Astronomy, Moon

Super Moon Dates

YearDate
2017Sunday, December 3
2018Monday, January 1
2019Monday, January 21
2019Tuesday, February 19

Super Full Moons can vary by time zone. Dates above are based on the local time in Washington DC. Change location

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The Moon

  1. What Is a Supermoon?
  2. The Moon Phases
  3. What Is a Micro Moon?
  4. Is a Blue Moon blue?
  5. The Moon's Orbit
  6. What Is a Black Moon?
  7. What Are Moonbows?
  8. Full Moon Names

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  1. The Lunar Month
  2. New Moon
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