A new, more precise measurement of the amount of deuterium, or heavy hydrogen, in the universe backs up previous work and the Big Bang theory for the origin of the universe.
A team of six astronomers used the 394-inch (10-meter) Keck telescope to observe a quasar (a distant and powerful young star) as it shone through an intervening intergalactic cloud. The wavelengths of light that made it through helped them determine that the cloud contained about one deuterium atom for every 40,000 normal hydrogen atoms.
This number, consistent with other independent measurements, gave the team confidence that they and other scientists are closing in on one of the most important pieces of evidence for proving the Big Bang theory.
"According to the theory, primordial deuterium was created by nuclear reactions in the first 1,000 seconds of the Big Bang," said David Tytler of the University of California, San Diego.
"The amount depends sensitively on the number of protons and neutrons present, so if we measure the deuterium, we can determine how many protons, and therefore how much matter is present in the universe."
The results were published in the May 10 issue of The Astrophysical Journal.
Deuterium clues
The method used by the team is considered to be the most accurate approach to measuring the elusive deuterium isotope of hydrogen because they are looking back in time to observe clouds in the early universe. Deuterium is destroyed by the formation and evolution of stars, so it is advantageous to search for deuterium in gas clouds while they are in a relatively pristine state.
This is the fourth measurement of this type undertaken by the team -- and the most accurate, said John O'Meara, the lead author on the paper.
"The other clouds were complex systems which made the observations more difficult to interpret," O'Meara said. "The fact that we found fair agreement with the other clouds makes the determination of primordial deuterium much more robust."
The result implies that in the first fraction of a second of the Big Bang, the universe was composed almost equally of matter and antimatter. For every 2 billion antiprotons, there were 2 billion plus one protons.
When combined with data from other types of telescopes and investigations, the following picture emerges. The universe is composed of 4 percent protons, electrons and other familiar particles, about 30 percent is in some mysterious, invisible form of matter called dark matter and about 66 percent is in a still more mysterious form of matter-energy called dark energy.
The team involved in this research also included David Kirkman, Nao Suzuki, Dan Lubin and Arthur Wolfe of UCSD's Center for Astrophysics and Space Sciences and Jason Prochaska of the Observatories of the Carnegie Institute of Washington. Some of the observations were also made with the Shane 118-inch (3-meter) telescope at the Lick Observatory.
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