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Monday, February 15, 1999 Published at 15:06 GMT


Sci/Tech

Haloes hang over South Pole

The halo and 'sun dogs' seen above the pole

By BBC News Online Science Editor Dr David Whitehouse

Scientists at the South Pole research base were dazzled recently by one of nature's most enchanting sights - sky haloes.


[ image: The haloes appeared fo 30 mins]
The haloes appeared fo 30 mins
Atmospheric haloes are caused by the reflection and refraction of sunlight by ice crystals high in the atmosphere.

The ice crystals alter the direction of the sunlight, or moonlight, passing through.

Different-shaped ice crystals alter the light's direction by differing amounts. In this way a 22 degree and/or a 46 degree halo can be formed.


[ image: The 22 and 46 degree haloes]
The 22 and 46 degree haloes
For 30 minutes, construction workers helping to rebuild the Amundsen-Scott research base station downed tools and joined researchers and other station personnel to observe and photograph at least 24 haloes that appeared.

Also seen in the photographs are parhelia or 'sun dogs.' These are patches of light on either side of the halo.


[ image: The haloes represent a rare allignment]
The haloes represent a rare allignment
Marko Pekkola, an expert on ice crystals stationed at the Pole, said that if all of the sighting claims are verified by photographic evidence, it would set a new world record for the number of haloes visible from a particular spot.

The South Pole is a good place to see them. Two of the three existing record halo displays were also sighted there in 1986 and 1990.



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