Supermoon: What is it and when can I see it?

A rare 'supermoon' will make the full lunar disc appear 14% bigger and up to 30% brighter than usual as it rises above the rooftops tonight.

Monday, 14th November 2016, 7:59 am
Updated Wednesday, 16th November 2016, 4:03 pm
A rare supermoon will make the full lunar disc appear 14% bigger and up to 30% brighter than usual as it rises above the rooftops tonight.

The event, described as "undeniably beautiful" by American space agency Nasa, is the result of the moon coming closer to Earth than it has done for 69 years.

Nothing will match it until the moon makes a similar approach on November 25 2034.

At 11.23am UK time on Monday the gap between the Earth and the moon will close to its shortest point, known as "perigee" - a distance of 221,525 miles (356,510 km).

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Sky watchers in the UK will have to wait a little longer before the full moon emerges in all its glory shortly before 5pm.

On top of the moon's bigger than usual size, they will then be treated to an additional "low-hanging moon" effect.

This is an optical illusion caused by the moon being close to the horizon, where it can be measured against familiar objects such as trees and houses.

Robin Scagell, vice-president of the Society for Popular Astronomy, said: "It will be above rooftops and trees and chimneys and always appears bigger that way because you're comparing it to foreground objects.

"I'm always pleased for people to get their binoculars out and look up at the craters and the seas."

The last time the moon was this close to the Earth was in 1948.

The reason the distance varies is the moon's slightly elliptical orbit.

On average, it is 238,900 miles (384,400 km) from the Earth, but at perigee it is about 5% closer.

At its furthest orbital point from the Earth, apogee, it is 5% more distant.

Perigee and apogee distances vary from month to month due to several factors, such as whether the long axis of the lunar orbit is pointed towards the sun.

Mr Scagell said the moon will appear only a fraction smaller on November 15.

"Supermoons" occur when a close approach is accompanied by a full moon.

Tonight's event is the biggest and best in a series of three supermoons. The first was on October 16 and the third is due on December 14.

Besides looking spectacular, the supermoon will give tides, which are affected by the gravity of the moon and sun, a small boost.

High and low tides usually reach their peak during a full or new moon.