Primordial "Heavy Hydrogen" Promotes
Big Bang Theory
May 16, 2001
Astronomers using the giant 10 meter Keck telescope have made the most
precise measurement to date of the amount of deuterium, or heavy
hydrogen, in the universe. This finding provides a stringent
constraint on the Big Bang theory for the origin of the universe.
Led by David Tytler of the University of California, San Diego, a team
of six astronomers observed absorption lines in light from a quasar.
Specific wavelengths of the quasar light were absorbed by various
types of atoms in an intervening, and very distant intergalactic cloud.
They determined that the cloud contained about one deuterium atom for
40,000 normal hydrogen atoms.
This number, which is consistent with other independent measurements,
gives the team confidence that they and other scientists are closing
in on one of the most important pieces of evidence for proving the Big
"According to the theory, primordial deuterium was created by nuclear
reactions in the first one thousand seconds of the Big Bang,"
explained Tytler. "The amount depends sensitively on the number of
protons and neutrons present, so if we measure the deuterium, we can
many protons, and therefore how much matter is present in the
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
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
relatively pristine state.
This is the fourth measurement of this type undertaken by the team.
According to John O'Meara, the lead author on the paper describing
the research which appeared in the May 10 issue of The Astrophysical
Journal, this result is the most accurate. "The other clouds were
complex systems which made the observations more difficult to
interpret," he said. "The fact that we found fair agreement with the
other clouds makes the determination of primordial deuterium much more
The result implies that in the first fraction of a second of the Big
Bang, the universe was composed almost equally of matter and
anti-matter. For every 2 billion anti-protons, 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 four percent protons, electrons and other familiar
thirty percent is in some mysterious, invisible form of matter called
dark matter, and about sixty-six 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 3 meter telescope at the Lick Observatory. This
research was supported by the National Science Foundation.
David Tytler (858) 534-7670
John O'Meara (858) 822-2018