Faintest stars among the jewels

Hubble's image of NGC 6397The Hubble telescope has opened a cosmic jewel box to reveal a collection of stars sparkling like diamonds.

Its stunning new photograph of a globular cluster called NGC 6397 is dazzling in its spendour. But it has also captured, between the brilliant jewels, what are believed to be the faintest stars ever seen in such a cluster.

The light from these dim stars is as faint as the glow of a birthday cake candle on the Moon as viewed from Earth.

NGC 6397 is a city of hundreds of thousands of stars and lies in the costellation of Ara. The stars look dazzling but their starlight has taken 8,500 years to cross space and reach the Earth.

Hubble’s picture was taken by a team led by Harvey Richer of the University of British Columbia, Vancouver, using the space telescope’s Advanced Camera for Surveys. Their results were announced to an international meeting of astronomers in Prague and will appear in today’s edition of the journal Science.

Richer said: “There are no fainter such stars waiting to be discovered. Any less massive ones faded early in the cluster’s history and by now are too faint to be observed.”

Globular clusters formed early in the 14 billion-year-old universe. Despite its great distance, NGC 6397 is actually one of the closest such cluster to Earth. Viewing the whole range of stars in the cluster will help astronomers to understand its age, origin and how it evolved.

Paul Sutherland

Paul Sutherland

I have been a professional journalist for nearly 40 years. I write regularly for science magazines including BBC Sky at Night magazine, BBC Focus, Astronomy Now and Popular Astronomy. I have also authored three books on astronomy and contributed to others.
Paul Sutherland

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Paul Sutherland

I have been a professional journalist for nearly 40 years. I write regularly for science magazines including BBC Sky at Night magazine, BBC Focus, Astronomy Now and Popular Astronomy. I have also authored three books on astronomy and contributed to others.

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