A Supermoon occurs whenever the Full Moon or New Moon arrives near its closest orbit of Earth – its perigee. Tonight’s Supermoon also happens to coincide with the New Moon stage of the lunar cycle. The New Moon is the start and end of one lunar cycle, which clocks in at about 29.5 days. When a Supermoon and New Moon appear on the same night, a rare Black Moon is born.
What is a Supermoon?
The Moon’s orbit around the Earth is not perfectly round but is instead elliptical.
As a result, the Moon is sometimes closer to us and sometimes farther away.
During a Supermoon event, the Moon approaches within 10 percent of its orbital perigee.
The perigee is the lowest point in the Moon’s orbit.
The opposite of the perigee, is the highest point or apogee.
A Full Moon or New Moon at apogee is known as a Micromoon.
US space agency NASA said: “The term ‘Supermoon’ was coined in 1979 and is often used today to describe what astronomers would call a perigean Full Moon: a Full Moon occurring near or at the time when the Moon is at its closest point in its orbit around Earth.”
The Moon’s perigee is about 253,000 miles (405,500 km) from Earth.
Will you be able to see the Supermoon tonight?
Unfortunately for hopeful astronomers, the Supermoon’s arrival on the day of the New Moon means the spectacle will not be seen.
The New Moon peaked today around 11.37am BST (10.37am UTC).
As a result, the Moon is no longer visible to the naked eye and its lit side faces away from us.
The Royal Observatory Edinburgh explained: “At the new Moon phase, the Moon is so close to the Sun in the sky that none of the side facing Earth is illuminated.
“In other words, the Moon is between Earth and Sun.”
The lunar phase is the result of the Moon’s orbit around the Earth.
The satellite takes approximately 27.3 days to circle the planet and the lunar cycle from one New Moon to the next lasts 29.5 days.
The Royal Observatory said: “The Moon spends the extra 2.2 days “catching up” because Earth travels about 45 million miles around the Sun during the time the Moon completes one orbit around the Earth.”