What is the Supermoon – The phenomenon explained

This November 14 was an event in every star gazer’s calendar as the world got to enjoy the brightest and most spectacular supermoon in almost 70 years. The phenomenon lit up the sky as it was the first time that a completely full moon has come this close to Earth since 1948. Anyone who didn’t catch a glimpse of the nightly sight will have to wait until 2034 when the next one is expected.

But what exactly is a “Supermoon”? According to scientists, this is a phenomenon that sees the moon slightly closer to Earth in its orbit than average, which leads to a particularly visible effect when this coincides with a full moon. This makes the moon appear bigger and brighter even though the difference in its distance from Earth is only a few percent at such times.

supermoon

Dr Daniel Brown, an astronomy expert at Nottingham Trent University, said: “Observing the supermoon is easier, as the moon remains visible throughout the entire night. As it is nearing winter, it will also be reaching its highest altitudes for the northern hemisphere.”

A supermoon phenomenon occurs when the full moon is within 10% of its closest approach to Earth, perigee, during its orbit. Despite not being particularly rare – coinciding with full moon is a very unusual occurrence and one that is worth observing. The gradual effect that happens once a month means that the moon will appear 14% bigger than its smallest size during the month.


Supermoons are known to bring larger tides because a closer Moon exerts a stronger gravitational pull and creates more variation between the tides. However, despite sensational newspaper titles – this variation is hardly enough to account for massive earthquakes, flooding, or volcanic eruptions.

The effects on Earth from the phenomenon are minor, and based on data from terrestrial seismologists and volcanologists, the combination of the moon’s proximity to Earth in its orbit, and being in its ‘full moon’ configuration (relative to the Earth and sun), does not have any significant effect on the internal energy balance of the Earth since there are lunar tides every day.

Coined by astrologer Richard Noelle in a 1979 article he wrote for Horoscope magazine, the term ‘Supermoon’ describes “a new or full moon which occurs with the Moon at or near (within 90 per cent of) its closest approach to Earth in a given orbit.”

Although originally this name didn’t get much traction, it has since become ubiquitous with skywatchers eagerly anticipating the next supermoon phenomenon.