"Primordial Deuterium and the Big Bang"ÃÂ Craig J. Hogan A Review h, the Greek letter eta, is used to describe the amount of matter in the universe. Eta is the ratio of how many protons there are for every neutron. Currently there is no agreement as to the precise value of eta, but Dr. Hogan's studies on deuterium may change that. Using high-powered telescopes and a lot of chemistry he and others have come up with a way of measuring the amount of matter in the universe using what they believe will be a constant ratio of deuterium to mass. Dr. Craig Hogan believes that his research will help to backup the already popular Big-Bang Theory on the birth of the universe.
Deuterium is a particularly heavy isotope that was only created within the first few minutes of the universe. According to the Big Bang theory, the universe began life around ten billion years ago in a fiery mess over 10 billion degrees Celsius.
The extreme heat and pressure of this "birth"ÃÂ was able to keep all of the subatomic particles that make up the universe to remain separated from each other. As the universe began to cool, just seconds after its birth, the temperatures dropped below 10 billion degrees and the subatomic particles were able to combine. The majority of the elementary particles formed protons and neutrons, with the more stable protons outnumbering the neutrons 7:1.
After a few minutes, the universe had cooled down to 1 billion degrees and the protons and neutrons were able to bond together. All of the protons and neutrons bonded together in 1:1 relationships to form deutrons. These deutrons in turn bonded with eachother to form primordial helium. Due to the lack of neutrons in the early universe, the majority of the protons had to stay isolated by themselves as Hydrogen. This explains the abundance of Hyrdogen in the universe.
In determining the amount of matter present in the universe scientists must find the universal constant h. h is the proportion between baryons (protons and neutrons) and photons. h is important in our understanding of the universes evolution and because it will allow us to compare things with the actual amount of matter present. Currently there is a discrepancy in the value of h, with values ranging by a multiplication of ten. By measuring cosmic background radiation we can determine the amount of photons present, but the exact numbers of baryons present is unknown. Elementally light particles offer the best guide to how many baryons are present in the universe and thus can help lead to h. Since deuterium is constantly being destroyed scientists must look for a place where elemental deuterium still exists as it may have had in the wee hours of the universe.
To find a place that existed as closely as possible to the original space, Dr. Hogan looked to quasars. These far away light sources shine through elemental gas clouds in space. Using light spectrum analyzers and huge telescopes, Hogan and some other have been able to find and measure the lyman lines (the colored lines on spectrum sheets) of the deuterium in the gas clouds. By measuring the quantity of deuterium in the gas clouds out in deep space scientists hope to find a more definite value of h.
In November 1993, Hogan and some colleagues were able to use the Keck telescope in Hawaii. Using this huge telescope they were able to for the first time come up with an accurate prediction of 1 deuterium atom in 5,000 atoms of hydrogen. Others later confirmed this number at the Kitt Peak National Observatory in Arizona.
Hogan is hopeful that there higher predictions are correct since these would match up correctly with the current predictions for the big bang model of one baryon per five billion photons. With more accurate numbers for n cosmologists will be able to make more accurate predictions of what happened 10-20 billion years ago.