Dark Age for astronomy as Hubble's window on the universe begins to close

Orbiting 350 miles above the Earth, it has been a window on to a universe that had previously existed only in the wildest imaginings of science fiction.

Since it went into orbit in 1990, the Hubble Space Telescope (HST) has beamed back awesome images of some of the most spectacular moments in the history of the universe. It has given us a ringside seat at the creation of an entire galaxy 10 billion years ago and at the Technicolor birth - and death - of a star.

And yesterday it was doing it again. The latest image taken from the Hubble takes us back almost to the beginnings of our universe's existence, towards a time that the Astronomer Royal, Sir Martin Rees, calls "the Dark Ages" - before there were any stars, and so no light.

The galaxy in the picture may be so far from Earth that the light from it reaching Earth now would have left 750 million years after the Big Bang, estimated to have occurred some 13 billion years ago; that is, when the universe was one-twentieth of its current age.

But the latest images could be among the last. Last month Nasa said there will be no more servicing missions to Hubble; instead Nasa will focus on the International Space Station. The cries of despair that have greeted this decision are light years from the mood when it all started.

Though mission scientists on the ground cheered when Hubble beamed back its first pictures on 29 May 1990, the astronomers at the Space Science Institute, set up to analyse Hubble's images, fretted. The pictures were simply out of focus. It was a catastrophe. Because the $1.5bn HST was orbiting above the atmosphere, it would have none of the distortion that earthbound astronomers suffer. But instead, it was just as bad.

Tests finally found that the HST had a manufacturing error in its main mirror, which captures the light that makes the pictures. It was wrongly curved - by two millionths of a metre. The mistake had not been detected during ground testing. The media had a field day.

The mirror was finally fixed in 1993 through a superhuman effort by Nasa astronauts, during a total of 35 hours' spacewalking. They also replaced failing gyroscopes needed to keep the telescope orbiting and pointed in the correct direction.

The results were fantastic, a panoply of images that have for 11 years delighted scientists and public alike.

But its Achilles heel remains its gyroscopes. They keep breaking down. In November 1999 four of its six gyros died, so that it had to be put into "hibernation". Luckily, a servicing mission had already been planned for the December.

But right now, only three are working. If another one dies, the telescope will once more have to hibernate. New challenges are at hand with President George Bush's call for human missions to the moon and Mars.

Nasa's rationale for ending missions to the HST is that they are more dangerous than visits to the Space Station. But leaked documents written by an engineer inside the agency show that Nasa considers Hubble missions safer - principally because there is far less "space junk" at the Hubble's height. (The ISS orbits about 250 miles up.)

Nasa insists that since last year's Columbia disaster, when damage on lift-off made the shuttle explode on re-entry, there must be provision to save astronauts on board a damaged shuttle. There is nowhere to stay on the Hubble; but the ISS is built to save people.

The problem, astronomers note, is that there is no telescope on the ISS.

For the latest images, the team at the California Institute of Technology (Caltech) which detected it say that the galaxy lies far beyond a cluster of stars called Abell 2218. It would not be visible at all but for a peculiarity of light, which - as Einstein predicted - can be bent by gravity: some of that shining from the new galaxy has been bent and magnified by the mass of Abell 2218's stars, a phenomenon which is known as gravitational lensing.

"As we were searching for distant galaxies magnified by Abell 2218, we detected a pair of strikingly similar images whose arrangement and colour indicated a very distant object," said Jean-Paul Kneib of the California Institute of Technology.

The distance to the objects was worked out by analysing their "red shift" - an analysis of their light which indicates how quickly they are moving away from us, and so how distant they are. Appropriately, it was the American astronomer Edwin Hubble, to whom the telescope was dedicated, who in 1929 first suggested that in our expanding universe, the further away a celestial object was, the more quickly that it would seem to be receding.

"The new object is a small and compact system of stars," said Professor Richard Ellis of Caltech. "It's about 2,000 light-years across; our own galaxy by comparison is about 60,000 light-years across. It is forming stars prodigiously and is a very energetic source, so it may be an example of an object from that early time [just after the 'Dark Ages'] that is the first of its kind to form in the Universe."

But he then went on to express his fears of a new Dark Age facing astronomers. Without servicing, the most precise telescope that humans have ever built will crash into the Pacific Ocean in 2007, instead of carrying on to 2010 or beyond.

"We need Hubble ... we could not have made this discovery without it," said Professor Ellis, who was explaining his institute's latest work at the annual meeting of the American Association for the Advancement of Science in Seattle.

"One of the instruments that would be placed on the telescope is a new infrared camera which would be perfect for the work we want to do. Many of us hope the decision to abandon further visits to Hubble will be examined very carefully because the scientific potential is very great," Dr Ellis said.

It is not only astronomers who are up in arms. An online "Save the Hubble" petition sprang up in October, when Nasa first began musing over the future of the telescope, and has attracted more than 25,000 signatures. But it was pressure from US senators which had a stronger effect, leading Mr O'Keefe to announce at the end of last month - barely two weeks after he formally announced that Hubble would receive no more servicing - that the decision would be "reviewed". But a week ago Nasa reiterated the original decision, more forcefully. Hubble will see no more astronauts.

Nasa has said that to compensate for the planned loss of Hubble it will try to speed up the launch of the James Webb Space Telescope, which is scheduled for 2011. But that is small compensation for scientists and a public around the world that had been accustomed to a wider view of the world. The new picture may have come from a time after the Dark Ages. But for astronomers, the picture beyond the next few years looks dark indeed.