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'Supermoon' to brighten up skies for stargazers
'Supermoon' to brighten up skies for stargazers
3/12/17
Skywatchers could catch a glimpse of a so-called "supermoon" - when the Moon appears larger and brighter in the sky as it moves closer to Earth - later.
It will appear about 7% larger and 15% brighter, although the difference is barely noticeable to the human eye.
The exact moment of the full moon will be at 15:47 GMT.
Robert Massey, of the Royal Astronomical Society, said it will appear brightest at midnight - when at its highest point above the horizon.
The Met Office's UK forecast suggests there will be clear spells this afternoon, so the supermoon may be visible.
December's full moon is traditionally known as the cold moon.
This full moon on Sunday afternoon - when it sits opposite the sun in the sky - will be 222,761 miles from Earth, closer than its average 238,900 miles.
Moon illusion
Mr Massey says the "most spectacular views" will come during moonrise, on Sunday, and moonset, on Monday morning.
This is because an optical illusion, known as the Moon illusion, makes it look unusually large when it appears close to the horizon.
In the UK, the moonrise will start just after 16:00 GMT - in Edinburgh it will rise at 16:15; in London at 16:21 and in Cardiff at 16:33.
Mr Massey said: "It's a nice enough phenomenon. It's always nice for people to go out and look at it.
"You won't necessarily think that it's huge. It will appear a bit bigger than usual, but don't expect it to look five times bigger."
A supermoon rises behind St Paul's Cathedral in London last year.
The moon doesn't move around Earth in a circle - it orbits in an elliptical or oval shape.
This means that its distance from Earth 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 as supermoons.
http://www.bbc.co.uk/news/uk-42211288
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