Skywatchers prepare for 'supermoon'

Skywatchers are preparing for the latest "supermoon" as Earth's satellite makes its closest approach since 1948, the BBC reports.

The UK's best chance to see it will be on Monday evening, although the Moon reaches its closest approach at 11:21 GMT when it will be 356,509 km away.

To observers, it will appear about 7% larger than normal and about 15% brighter - although the human eye is barely able to discern that difference.

Yet the Moon won't be this close again until 25 November 2034.

The Met Office's UK forecast suggests it will be cloudy when the supermoon is closest, although it advises people to check their local forecast for the event.

As the Moon traces its orbit around the Earth, we see different proportions illuminated by the Sun. Once in each orbit, our satellite is totally illuminated - a full moon.

And as the Moon orbits the Earth every 27 days or so, it travels in an elliptical or oval shape.

This means that its distance from our planet is not constant but varies across a full orbit.

But within this uneven orbit there are further variations caused by the Earth's movements around the Sun.

These mean that the perigee - the closest approach - and full moon are not always in sync.

But occasions when the perigee and full moon coincide have become known in popular parlance as supermoons.

To observers, the differences between a supermoon and a normal full moon are quite subtle.

Generally, supermoons can be up to 14% larger and 30% brighter, but only when compared with the furthest point the Moon gets to within its orbit.

"These differences are pretty small, and with the Moon rising so high in the sky, as it does in the winter months, it'll be quite hard to notice any difference without comparing photographs," Dr Chris North told The Conversation website.

"But regardless of how big and bright it looks, the Moon really is a beautiful object to look at."

However Neil de Grasse Tyson, director of the Hayden Planetarium in New York, has previously suggested the events are just a little bit over-hyped.

"I don't know who first called it a supermoon," he told StarTalk radio.

"I don't know, but if you have a 16-inch pizza, would you call that a super pizza compared with a 15-inch pizza?"