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Friday, 14 April, 2000, 16:07 GMT 17:07 UK
Ten years of Hubble science
The distorted light of Abell 2218
It was a promise fulfilled. After its spectacular repair in 1993, the Hubble Space Telescope (HST) had a clear and unhindered view of the cosmos and it was not long before its images were astounding astronomers.

Whether it is the dust storms on Mars, the birth of stars, galaxies, black holes or the edge of the Universe, Hubble will have a remarkable picture of it.

deep impact
Deep impact: Comet Shoemaker-Levy 9 hits Jupiter
In 1994, it witnessed the shattered remnants of Comet Shoemaker-Levy 9 smashing into Jupiter. The pictures of a dark blemish spreading over Jupiter's gaseous surface are unique.

One of its most spectacular observations was of the giant cluster of galaxies called Abell 2218. This is a collection of galaxies whose gravity distorts the light from more distant objects.

This so-called "gravitational lens" effect creates remarkable arcs of smeared light. Studying them yields important clues about the size and evolution of the Universe.

Truly amazing

Professor Richard Ellis, of the University of Cambridge, told BBC News Online about the time he first saw the image.

Hubble history
1977 - Project begins
1985 - Hubble built
1990, 24 April - Hubble launched
1990, 18 May - First light
1993, December - Flaw repaired
2000, 24 April - 10 years of Hubble
2010 - End of Hubble mission
"I remember it as going in to work over the weekend and waiting patiently for the people in Baltimore to give us the data. Then we got it and we went 'wow, gosh, this is truly amazing.'

"We were amazed because there were all these arcs. One saw gravity at work for the first time. Even the untrained eye could see that there was something spectacular going on. The arcs were very thin and sharp and beautifully concentric around the cluster.

"It was one of the most vivid demonstrations of the bending of light by massive objects and it became a classic."

Professor Ellis and colleagues were able to follow up this image with other ground-based telescopes and measure the sizes of all the arcs.

Deep field

For many people, the HST's most extraordinary picture is either the so-called Eagle nebula or the Hubble Deep Field.

Eagle nebula
Eagle nebula: An all-time great

The Eagle nebula is a vast cloud of gas and dust in which stars are being formed. The HST saw three towering columns of gas containing bright points, each of which was larger than our own Solar System.

"When I saw this image it just blew me away," says astronomer Jeff Hester.

The other observation, the Deep Field, has been called a "bore-hole" through the cosmos. Hubble stared at an apparently blank patch of sky for hundreds of hours in an attempt to peer to the very edge of the Universe.

The resulting picture has become one of the scientific icons of our age. It shows thousands of young galaxies. It is a glimpse of the dawn of the Universe.

The death of stars

Dr Mario Livio of the Space Telescope Science Institute told BBC News Online: "Hubble has also provided many spectacularly detailed and visually stunning images of stellar deaths.

"For one very massive star called Eta Carinae, which is over a hundred times the mass of our Sun, we have seen that it has blown out large gas clouds either side of it, like an hourglass.

Supernova 1987a
Big birth: Supernova 1987a
"And Hubble has produced some truly breathtaking images of the gas clouds produced when stars lose their outer layers. Like snow flakes, each one is different."

Supernova 1987a is a star that was seen to explode in a companion galaxy to our Milky Way in 1987. It was a so-called supernova explosion, the closest witnessed since the telescope was invented.

University of Colorado astronomer Dick McCray told BBC News Online: "Hubble has observed a remarkable triple ring system around supernova 1987a meaning that for the first time we are observing the birth of a supernova remnant and seeing things change in space on a human timescale."

How old, how big?

But if Hubble was built for anything it was to answer one question. How old is the Universe?

Wendy Freeman of the Carnegie Observatories in California told BBC News Online: "Before Hubble was launched, astronomers couldn't measure the size of the Universe to better than a factor of two. One of the biggest challenges for measuring the age and size of the Universe is to measure very accurate, remote distances."

Cepheids: The stellar signposts

The HST was to do that by looking for stellar signposts called Cepheids. These are stars that vary their light output in a way that depends upon their absolute brightness. It means that they can be used to measure distances.

Professor Freeman says: "Hubble measured Cepheid variable stars 10 times further away than was possible before and now about 30 galaxies have had their Cepheid distances measured.

"We now know the age and size of the Universe to an accuracy of 10% [ - about 13.7bn years]. Hubble has achieved what it set out to do."

Words by Dr David Whitehouse; Images courtesy of the Space Telescope Science Institute

Hubble SlideShow
See also:

14 Apr 00 | Science/Nature
14 Apr 00 | Science/Nature
14 Apr 00 | Science/Nature
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