First light: astronomers use distant quasar to probe cosmic 'dark age,' universe origins

August 07, 2001

Using light from the most distant object known, astronomers have found traces of the first generation of atoms in the universe, 14 billion light years from Earth. The observations are the first of the cosmic "Dark Age" between the Big Bang and the first visible stars and galaxies and allow astronomers to set a date for the complete reionization of the universe.

The observations, by Robert Becker of the University of California, Davis, and the Lawrence Livermore National Laboratory, Xiaohui Fan of the Institute for Advanced Study in Princeton, Michael Strauss of Princeton University, and Rick White of the Space Telescope Science Institute, a team of scientists with the Sloan Digital Sky Survey, mark the point when radiation from the first stars and quasars tore apart and reionized -- the neutral hydrogen atoms that filled space after the Big Bang.

"The history of these atoms has been part of the unknown territory of cosmology," said UC Davis cosmologist Becker.

All space, time, and energy began with the Big Bang. As the universe cooled, energy turned into matter. Quarks and electrons, then protons and neutrons appeared in the first minute. But at temperatures of 1 billion degrees, it was too hot for complete atoms to form. Scientists have found that it took another 300,000 years for the temperature to cool off enough for whole atoms of hydrogen to appear.

The half billion years between the formation of these first atoms and the creation of the most distant light-emitting objects detected by astronomers remains shrouded in mystery. Astronomers have dubbed this period the cosmic Dark Ages. We do know, however, that all was not quiet in these early times. Cosmic background radiation from the period of atom formation shows that matter was smoothly distributed through the universe, said Becker. By the end of the Dark Ages, matter was clumped into massive structures such as the billion-solar mass black holes powering the quasars detected in the new observations.

In addition, while the Big Bang created only hydrogen, helium and a trace amount of lithium, the quasar light reveals traces of more complex atoms including carbon, nitrogen, oxygen and silicon, all of which had to be cooked up in stars out of the primordial material.

At the end of the Dark Ages, hydrogen atoms were ionized again, or stripped into atomic nuclei and electrons. This reionization was probably caused by ultraviolet light from the first quasars and stars. Until now, the timing of this reionization event has been uncertain.

In 1965, Jim Gunn and Bruce Peterson, then at the California Institute of Technology predicted that the neutral atoms would be detected by their light-absorbing signature, creating a trough in the spectrum. Hydrogen atoms absorb all the light at a particular, characteristic wavelength, Becker said. If at least one part in a 100,000 of the hydrogen in intergalactic space were made up of whole atoms, all the light at this wavelength would be blocked, he said.

"Seeing the effects of neutral hydrogen in the spectrum of this quasar is telling us that we're finally probing the universe to a time when the first stars and quasars lit up," said Gunn, now at Princeton University and the project scientist of the SDSS. "Scientists have been looking for this for a very long time; it is tremendously gratifying that we are finally seeing it."

Because light from objects that are distant in space and time is shifted toward the red end of the spectrum, the Gunn-Peterson trough would also be shifted, Becker said. By looking at where in the spectrum the trough occurred, astronomers could tell how old those atoms were, he said.

To achieve this, astronomers have to look at objects billions of light years away and therefore far back in time. But in 35 years, no one has been able to detect the Gunn-Peterson effect, Becker said. The conclusion was that almost all of the hydrogen in intergalactic space is ionized.

"Only now have we found a quasar that is far enough away," Becker said.

Using the powerful Keck telescope on Mauna Kea in Hawaii, Becker and his colleagues detected the imprint of neutral atoms on light from quasar J1030+0524. J1030 is the most distant object yet found, at 14.5 billion light years from Earth. It was discovered in April this year by the Sloan Digital Sky Survey scientists, led by Fan.

The researchers spread out the recorded light into its constituent wavelengths. They found that, over a region of the spectrum corresponding to millions of years of cosmic history, no light from the quasar gets through -- it is all absorbed in intergalactic space.

"The culprits responsible are from the very first generation of atoms. These observations provide our first glimpse at truly primordial material, and constrain the time at which the reionization of the universe took place," Becker said.

The results will be submitted to the Astronomical Journal. The Keck observatory, which houses the world's largest telescope, is jointly managed by the California Institute of Technology, the University of California, and NASA. The Sloan Digital Sky Survey aims to map in detail one quarter of the sky and 200 million celestial objects. Funding for the Sloan Digital Sky Survey has been provided by the Alfred P. Sloan Foundation, the participating institutions, the National Aeronautics and Space Administration, the National Science Foundation, the U.S. Department of Energy, the Japanese Monbukagakusho, and the Max Planck Society. The Sloan Digital Sky Survey is a joint project of The University of Chicago, Fermilab, the Institute for Advanced Study, the Japan Participation Group, The Johns Hopkins University, the Max-Planck-Institute for Astronomy (MPIA), the Max-Planck-Institute for Astrophysics (MPA), New Mexico State University, Princeton University, the United States Naval Observatory, and the University of Washington.
More information:

Media contacts:

  • Robert Becker, UC Davis Physics and LLNL, (925) 423-0664,
  • Rick White, STSCI, (410) 338-4899,
  • Michael Strauss, Princeton, (609) 258-3808
  • Georgia Whidden, IAS Press Office 609-734-8239,
  • Stephen Schultz, Princeton News Service, (609) 258-3601,
  • Anne Stark, Lawrence Livermore National Laboratory, (925) 422-9799, stark8@llnl.go

    University of California - Davis

    Related Hydrogen Articles from Brightsurf:

    Solar hydrogen: let's consider the stability of photoelectrodes
    As part of an international collaboration, a team at the HZB has examined the corrosion processes of high-quality BiVO4 photoelectrodes using different state-of-the-art characterisation methods.

    Hydrogen vehicles might soon become the global norm
    Roughly one billion cars and trucks zoom about the world's roadways.

    Hydrogen economy with mass production of high-purity hydrogen from ammonia
    The Korea Institute of Science and Technology (KIST) has made an announcement about the technology to extract high-purity hydrogen from ammonia and generate electric power in conjunction with a fuel cell developed by a team led by Young Suk Jo and Chang Won Yoon from the Center for Hydrogen and Fuel Cell Research.

    Superconductivity: It's hydrogen's fault
    Last summer, it was discovered that there are promising superconductors in a special class of materials, the so-called nickelates.

    Hydrogen energy at the root of life
    A team of international researchers in Germany, France and Japan is making progress on answering the question of the origin of life.

    Hydrogen alarm for remote hydrogen leak detection
    Tomsk Polytechnic University jointly with the University of Chemistry and Technology of Prague proposed new sensors based on widely available optical fiber to ensure accurate detection of hydrogen molecules in the air.

    Preparing for the hydrogen economy
    In a world first, University of Sydney researchers have found evidence of how hydrogen causes embrittlement of steels.

    Hydrogen boride nanosheets: A promising material for hydrogen carrier
    Researchers at Tokyo Institute of Technology, University of Tsukuba, and colleagues in Japan report a promising hydrogen carrier in the form of hydrogen boride nanosheets.

    World's fastest hydrogen sensor could pave the way for clean hydrogen energy
    Hydrogen is a clean and renewable energy carrier that can power vehicles, with water as the only emission.

    Chemical hydrogen storage system
    Hydrogen is a highly attractive, but also highly explosive energy carrier, which requires safe, lightweight and cheap storage as well as transportation systems.

    Read More: Hydrogen News and Hydrogen Current Events
  • is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to