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What is a Supermoon and When is the Next One?

A Supermoon happens when there's a full Moon or a new Moon at the same time as the Moon's approach to its perigee – the point on its orbit closest to the Earth. It is also known as Super Full Moon, Super New Moon and Perigee Moon.

Wat arun in night with super full moon
A Supermoon can be full or new.
A Super Full Moon looks no different than any other full moon, it's just a bit closer to Earth.
©bigstockphoto.com/Prasit Rodphan

The next Supermoon that occurs on Monday, September 28, 2015 is a special one – it will be be totally eclipsed for over 3 hours. This Total Lunar Eclipse is the last one in a tetrad of total eclipses of the Moon, also known as Blood Moons.

Locations 2 and more hours behind UTC, will be treated to the Supermoon and the Total Lunar Eclipse on the night of Sunday, September 27, 2015. These locations include all of the United States, Canada, and South America.

Upcoming Supermoons

2015Sunday, September 27
2016Monday, November 14
2017Sunday, December 3

Elliptical Orbit

The Moon's orbit around the Earth is not a perfect circle, but elliptical, with one side of the orbit closer to the Earth than the other side. The point on the Moon's orbit close to the Earth is called the perigee and the point farthest away is the apogee.

The elliptical path that the Moon takes around the Earth during a lunar month – the period between two successive full Moons or new Moons – means that the distance from Moon to Earth varies throughout the month and the year. On average the distance is about 238,000 miles or 382,900 kilometers.

Moon Phases worldwide

Super Full Moons, Super New Moons and Micro Moons

When a full Moon or new Moon coincides with being closest to Earth, it is called a supermoon, Super Full Moon, or Super New Moon.

A Micro Moon on the other hand, occurs when a full or a new Moon takes place at the same time the Moon is farthest from the Earth or at its orbital apogee. It is also sometimes known as a Minimoon, Mini Full Moon or a Mini New Moon.

There are currently no 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.

timeanddate.com uses the following definition:

  • Supermoon: A full or new Moon that occurs when the Moon is less than 360,000 kilometers (ca. 223,694 miles) from the center of the Earth.
  • Micro Moon: A full Moon or new Moon that takes place when the Moon is farther than 400,000 kilometers (ca. 248,548 miles) from the Earth.

Bigger and Brighter

Full moon setting over Jobs Peak, Carson Valley, Nevada.
A full Moon near the horizon looks bigger and brighter than when the same full Moon is higher in the Sky.
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

Due to its proximity to the Earth, a Super Full Moon appears about 7% larger than an average full Moon. When compared to a Mini Full Moon, it looks about 12% larger.

Fun fact: 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, the 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 larger than summer Perigee Moons.

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

Full Moons that occur before and after a Super Full Moon tend to also be bigger and brighter than an average full Moon. These full Moons are also often called Supermoons by many media outlets.

When and How to View a Supermoon

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 Supermoon will look bigger and brighter than when it is higher up in the sky because observers are able to compare the apparent size of the Supermoon with elements in the landscape – hills, foliage and buildings. This effect is popularly called the Moon illusion.

Technical Name: Syzygy

Supermoon is not a term widely used by astronomers or scientists. It was first coined by 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.

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

Tidal Effects

Tides on Earth are caused by the gravitational pull of the Moon.
Tides are caused by the Moon's gravitational pull.
Tides are caused by the Moon's gravitational pull.

The tides on Earth are mostly generated by the intensity of the Moon’s gravitational pull from one side of the Earth to the other. The Moon’s gravity can cause small ebbs and flows in the continents called land tides or solid Earth tides. These are greatest during the full and new Moons because the Sun and Moon are aligned on the same or opposite sides of the Earth.

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 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. There is a small difference in tidal forces exerted by the Moon’s gravitational pull at lunar perigee. However, the difference is too small to overcome the larger forces within the planet.

Topics: Astronomy, Moon

Next Partial Solar Eclipse: Sun, Sep 13, 2015 … See animation

In this Article


All about the Moon

  1. Moonphases worldwide
  2. Phases of the Moon
  3. What is a Supermoon?
  4. Micro Moon versus Supermoon
  5. Is a Blue Moon blue?
  6. The Moon's orbit
  7. What is a Black Moon?
  8. What are Moonbows?
  9. Full Moon names

Moon index

Moon Phases in your city

Moonrise & Moonset times

Eclipse Lookup

Weather lookup

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