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Tuesday, January 27, 1998 Published at 19:03 GMT



Sci/Tech

'Blinkers' on the sun
image: [ A close-up of a section of the sun's surface before, during and after a blinker explosion (RAL) ]
A close-up of a section of the sun's surface before, during and after a blinker explosion (RAL)

A British-led team of astronomers has discovered a new phenomenon on the sun -- short-lived explosions, each the size of the Earth, dubbed "blinkers".

At any one time, a rash of around 3,000 blinkers are breaking out all over the sun's surface. Each explosion has the power of 100 megatons, equivalent to nearly seven large hydrogen-bombs.

Scientists believe the previously unobserved blinkers may help them find the answers to key questions about the sun, such as where the solar wind comes from and why its outer atmosphere is so much hotter than the surface.


[ image: At any one time the sun is mottled with about 3,000 explosions, each the size of the earth (RAL)]
At any one time the sun is mottled with about 3,000 explosions, each the size of the earth (RAL)
The explosions were detected by an instrument aboard a European Space Agency sun-observing satellite, built and operated by scientists at the Rutherford Appleton Laboratory in Didcot, Oxfordshire.

Chief investigator Dr Richard Harrison, from the RAL, said: "This is a brand new phenomenon.

"When you look at the sun in ultraviolet light frequencies it has a granular appearance, like an orange. Home in on a piece of the orange and you see these flashes.

"They produce radiation in the extreme ultraviolet, between the level of UV and X-rays, and may have a temperature of up to a million degrees centigrade.


[ image: The SOHO satellite]
The SOHO satellite
"We think they cover the sun constantly, like a kind of global disease. It's what we've been looking for to help us solve mysteries we don't know the answers to."

The blinkers may be part of the process that gives rise to the solar wind -- the constant stream of atomic particles flowing out from the sun at up to 600 miles per second.

They may also help account for why the sun's outer atmosphere, the corona, is heated to more than one million degrees C when the surface is only 5,500 C.

The satellite which made the discovery is the Solar and Heliospheric Observatory (SOHO) launched on December 2, 1995, and placed in an orbit around the sun.

Dr Harrison is principal investigator for the Coronal Diagnostic Spectrometer on SOHO which detected the blinkers. The discovery is shortly to be published in the journal Solar Physics.
 





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  Internet Links

Royal Astronomical Society press release

Rutherford Appleton Laboratory solar physics site

SOHO Satellite pictures of blinkers

Solar and Heliospheric Observatory


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