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Friday, June 25, 1999 Published at 15:07 GMT 16:07 UK


Gemini images rival space telescope

Definition 'right at the limits'

The sharpest images of the Universe ever taken by a ground-based telescope have been unveiled.

The pictures were recorded by astronomers using the giant Gemini North telescope in Hawaii, which was inaugurated on Friday.

They show stars in a globular cluster 50,000 light years away.

Gemini North is one of a pair of telescopes. Its twin, Gemini South, is being built in Chile and will become operational in a year's time. Together, the two telescopes will offer unparalleled views of the entire sky.

[ image: Hawaii offers best skies on Earth]
Hawaii offers best skies on Earth
Clever electronics allow each telescope's eight-metre (26 ft) -wide mirror to compensate for the distorting effects of the Earth's atmosphere.

Mounted behind the mirror are 120 "actuators" that constantly adjust the mirror. These adjustments are typically only about 1/10,000 the thickness of a human hair and are enough to keep starlight precisely focused.

The resulting images are as clear as those obtained from the Hubble Space Telescope.

[ image: First ever Gemini pictures - Pluto and its moon Charon]
First ever Gemini pictures - Pluto and its moon Charon
"A few years ago, the possibility of seeing these stars so clearly with a ground-based telescope would have been regarded as highly speculative, but with Gemini we are seeing some pictures with more detail than Hubble can provide at a fraction of the cost," said British Gemini scientist Dr Patrick Roche.

Inside dust clouds

Gemini will be particularly suited for investigating the origins of stars and galaxies.

The enormous light collecting power of each giant mirror will allow Gemini to see fainter objects further away than ever before.

[ image: Gemini can see stars being born]
Gemini can see stars being born
A special silver coating will make the optics sensitive to infrared light, allowing astronomers to pierce the clouds of dust which normally obscure star nurseries.

The reflective surface of each mirror is so accurate that if the mirror was the diameter of the earth, the largest defect on its surface would be less than 30cm (1 ft) high.

The two Gemini telescopes have been built by an international consortium which includes astronomers from the US, the UK, Canada, Chile, Argentina and Brazil. The UK has contributed a third of the £100m cost.

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