White Continent to go black

By Lucy Rogers

Penguins, scientists and keen astronomers will be among a select few to experience this Sunday's total eclipse of the Sun in Antarctica.

The 500-kilometre-wide shadow of the Moon will sweep across the southern Indian Ocean and the frozen wastes of the White Continent at speeds exceeding one km per second.

Eclipse chasers have paid thousands to get to Antarctica

It will take about one hour to cover the 5,000-km-length of the path. But for those viewing from the ground, the time of totality - when the Moon completely blocks the Sun - will be less than two minutes.

Solar eclipses usually take place once every year or two and always at new Moon - when the lunar body sits directly between the Sun and the Earth.

However, it does not happen every new Moon. The lunar orbit is slightly tilted to that of our planet and therefore "the Moon's shadow often misses the Earth," says Fred Espenak, a Nasa astrophysicist.

Mr Espenak, or "Mr Eclipse" as he is better known, works at the US space agency's Goddard Space Flight Center.

Super Sun

He has participated in nearly 20 eclipse expeditions around the world and made predictions on thousands.

"A total eclipse of the Sun is simply the most awe-inspiring sight in all of nature," he said. "Once seen, it can never be forgotten".

But Mother Nature is seemingly shy about showing off her glory. The next time she puts on this astronomical display will be April 2005, when it will be visible only in the middle of the Pacific Ocean.

No photograph can really come close to what the human eye can see during a total eclipse Fred Espenak, Nasa

The rarity of these events is one reason why eclipse chasers - astronomers who travel all over the world for a glimpse of this celestial spectacle - have paid thousands of pounds for tickets to see this Sunday's show.

Weather permitting, the observers will have a lot to look at in their two minutes. Around the horizon will be a twilight - though not as dark as night. It will be similar to the sky about 30 minutes before Sunrise or after Sunset.

The planets Mercury, Venus and Jupiter will all be visible to the naked eye. Bright stars, including Betelgeuse and Rigel in the constellation of Orion, will also be on show.

None better

But the most significant thing about a total eclipse is being able to see the solar corona - the outer atmosphere that surrounds the Sun.

"It is the only time you can gaze upon the solar corona - a super heated plasma of about two million degrees Fahrenheit," said Mr Espenak. "You see unbelievable structures in unbelievable detail."

Photographs and television pictures are poor representations of what can be seen.

"No photograph can really come close to what the human eye can see during a total eclipse," said Mr Espenak.

"Your eye has such a great dynamic range that you can see the very brightest part as well as the much fainter outer parts of the corona all at once, whereas a photograph can only capture a very narrow dynamic range in any one exposure."

Using a solar filter - a thin sheet of specially developed film that blocks most of the glare from the Sun - it will be possible to see the Moon beginning to cover the Sun.

The partial eclipse will last for about an hour from first contact - when the Moon starts to nibble away at the solar disc - until totality.

Dazzling diamond

When the Moon covers 90-95% of the Sun, the sky will start to get dark. Shadows will look odd. If the hand is held one way, the shadows of the fingers will appear very long and thin, as if a low winter's Sun is in the sky.

However, if the hand is swivelled around, they will become short and thick, as if the Sun was directly overhead.

There will be a rapid drop of temperature leading up to totality. Although, whether this will be noticed when it is already well below freezing in Antarctica is questionable.

In the last 10-20 seconds before totality, as the last sunshine streams between the mountains on the Moon, a string of lights known as Baily's Beads will be visible. But even these will wink out one by one until just one dazzling bright diamond remains.

And then the Sun is gone.

The shadow of the Moon will dash over the horizon towards the observers at incredible speed. Suddenly there will be a very eerie darkness - before the whole sequence goes into reverse.

Afterwards, according to Mr Espenak, observers will turn to each other and say "that was great - when's the next one?"

The Sun should never be looked at directly with the naked eye or through a telescope or binoculars, as this can cause blindness.