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Fw: Hubble's deepest shot is a puzzle

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  • Amy Harlib
    aharlib@earthlink.net ... Amy
    Message 1 of 1 , Oct 3, 2004

      > They've a nice graphic at the end of the article; follow the link to see
      > it.
      > ----------------------------------
      > http://news.bbc.co.uk/1/hi/sci/tech/3680944.stm
      > Hubble's deepest shot is a puzzle
      > Scientists studying the deepest picture of the Universe, taken by the
      > Hubble Space Telescope, have been left with a big poser: where are all the
      > stars?
      > The Ultra Deep Field is a view of one patch of sky built from 800
      > exposures.
      > The picture shows faint galaxies whose stars were shining just a few
      > hundred million years after the Big Bang.
      > But the image's revelation that fewer stars than expected were being born
      > at this time brings into question current ideas on cosmic evolution.
      > "Our results based on the Ultra Deep Field are very intriguing and quite
      > a puzzle," says Dr Andrew Bunker, of Exeter University, UK, who led a team
      > studying the new data.
      > "They're certainly not what I expected, nor what most of the theorists in
      > astrophysics expected."
      > He is now urging the US space agency (Nasa) to proceed with a servicing
      > mission to upgrade the orbital telescope so it can solve the mystery.
      > A 'fried' Universe
      > At issue is the timing of key events in the earliest stages of the
      > Universe.
      > Scientists believe the super-hot conditions that existed after the Big
      > Bang eventually cooled sufficiently to allow protons, neutrons and
      > electrons to form neutral atoms of hydrogen and helium.
      > The transition also saw the cosmos plunge into darkness - the stars that
      > could provide the light had yet to ignite.
      > When they did, from infalling clouds of hydrogen and helium, the "dark
      > ages" gave way to what has been dubbed the "cosmic renaissance".
      > What is more, these hot, young stars produced intense ultraviolet
      > radiation which "fried" the gas in the Universe - to produce the diffuse
      > intergalactic plasma detectable today.
      > But the Hubble Ultra Deep Field presents a problem for this story.
      > When Bunker and colleagues measured the rate of star formation in the
      > image's earliest galaxies, they found it was insufficient to create the
      > levels of radiation needed to produce the intergalactic plasma.
      > "There is not enough activity to explain the re-ionisation of the
      > Universe," Dr Bunker told the BBC. "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."
      > Red search
      > The Hubble data was supported by observations with the Keck telescope in
      > Hawaii and the Gemini telescope in Chile.
      > It has to be said, the Bunker assessment is not totally shared by all
      > groups working in this area. Four other teams investigating the UDF data
      > have put their own very different interpretations on what they see in the
      > historic image.
      > For example, the team headed by Dr Massimo Stiavelli, from the Space
      > Telescope Science Institute, in Baltimore, US, believes the populations
      > seen may well have been able to re-ionise the Universe, provided the stars
      > were bigger and possessed much fewer heavier elements than those we see
      > today.
      > But what all astronomers believe is that to solve this puzzle, they need
      > enhanced space-borne detectors that can better describe the
      > long-wavelength light seen in the most distant stars.
      > The Hubble telescope will get this capability if Nasa goes ahead with a
      > servicing mission and installs an instrument known as the infrared
      > WideField Camera 3.
      > This is by no means certain, however, and astronomers may have to wait for
      > the launch of Hubble's successor, the James Webb Telescope, early in the
      > next decade.
      > "For the first time, we at last have real data to address this final
      > frontier - but we need more observations," said Dr Richard Ellis, of the
      > California Institute of Technology, US, who is passionate in his support
      > of a mission to upgrade Hubble.
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