Friday, December 12, 2008

Earth enjoys full moon close-up

Full moon over San Francisco
The moon will appear high in the night sky

A full moon has occurred closer to the Earth than it has done at any time for the past 15 years.

The Moon's elliptical orbit means its distance from the Earth is not constant.

It was a little over 350,000km away as it passed over the northern hemisphere, about 30,000km closer than usual.

Astronomers said the moon would appear brighter and larger than usual, but the sky in the UK was almost completely covered by cloud.

Closest path

Friday's full moon was predicted to appear up to 14% bigger and 30% brighter than other full moons this year, according to Nasa.

The Moon's orbit is elliptical, meaning it does not follow a circular but rather an oval path.

It has reached the point where this oval orbit is nearest to the Earth.

"It's only every few years that a full moon happens to coincide with the part of the Moon's orbit when its closest to the Earth," said Marek Kukula, an astronomer at the UK's Royal Observatory.

The moon appears largest as it rises and sets, but this is a psychological illusion, Dr Kukula said.

"When it's close to the horizon, our brain interprets it as being bigger than it actually is, this is called the moon illusion," he said.

"The size may be striking when it's near the horizon," said Robert Massey of the UK Royal Astronomical Society.

However, he cautioned against expecting too much.

"The Moon may be brighter and may appear somewhat larger, but it's really quite hard for the eye to notice the difference; the eye will compensate for the extra brightness, it's not like going from night to day," said Dr Massey.

The Moon's brightness varies throughout its annual cycle, during the mid-winter in the northern hemisphere it can appear brighter simply because it is higher in the sky. from BBC.

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