Brussels, 24 Sep 2004
The Hubble Space Telescope has provided astronomers with the deepest and most sensitive view of the distant Universe ever obtained, offering an insight into some of the earliest star forming galaxies.
Hubble's Ultra Deep Field (HUDV) can peer 95 per cent of the way back to the Big Bang, picking up the faint light of galaxies that shone when the Universe was only hundreds of millions of years old, and which has spent the intervening 13 billion years reaching Earth.
A team led by Andrew Bunker at the University of Exeter, UK, carried out an analysis within a day of the data being made available by the US national aeronautics and space administration (NASA). Their results will be published in the journal 'Monthly notices of the Royal Astronomical Society'.
Dr Bunker and his colleagues identified 50 likely galaxies from the HUDF data. One member of the team, Elizabeth Stanway from Cambridge University, explained: 'Intervening gas clouds absorbed visible light from these galaxies long before it reached Earth, but their infrared light can be detected, and it is their infrared colours which lead us to believe that these galaxies lie at such immense distances.'
The astronomers used two of the largest Earth based telescopes, the ten metre Keck telescope in Hawaii and the eight metre Gemini instrument in Chile, to verify the HUDF data. 'Using the largest optical telescope, Keck, was very important as it showed that this population of objects discovered by the Hubble Space Telescope really are incredibly distant,' said Dr Bunker.
However, rather than providing answers to unsolved mysteries, this unprecedented view of the early Universe has posed a new question. In their analysis, the UK team found significantly fewer stars than they expected at this stage in the development of the Universe.
This casts a certain amount of doubt over our current understanding of the early stage development of the Universe. Scientists believe that when the very first stars were formed by the gravitational collapse of inert clouds of hydrogen and helium atoms, the ultraviolet radiation they produced helped to 'fire' the neutral gases that remained, creating the intergalactic plasma that we see today.
However, as Dr Bunker told the BBC, the data from Hubble suggests that the rate of star formation in these earliest galaxies was insufficient to create the necessary levels of radiation to produce the plasma: 'There is not enough activity to explain the re-ionisation of the Universe. Perhaps there was more action in terms of star formation even earlier in the history of the Universe - that's one possibility.'
'Another exciting possibility is that physics was very different in the early Universe; our understanding of the recipe stars obey when they form is flawed,' he speculated.
Not all scientists in this field agree with Dr Bunker's assessment, however, and it appears that the only way this question will be resolved is if NASA proceeds with a servicing mission to upgrade the Hubble telescope. Given that this mission is still far from assured, scientists may have to wait until Hubble's successor, the James Webb Telescope, is launched early next decade.