Astrophysics and Cosmology
Searching for clues to the early universe
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| Brad Johnson, a graduate student in Shaul Hanany's group, works on the MAXIMA balloon-borne telescope prior to its launch. |
| photo courtesy MAXIMA web site |
Researchers in Cosmology and Particle Astrophysics seek to understand the early universe by looking for the remnants of the Big Bang. Many of them work collaboratively with faculty in the Astronomy department (which shares a building with Physics). On the experimental side, this involves building devices to detect particles and radiation. Professor Shaul Hanany leads an experimental research group that measures cosmic microwave background (CMB) radiation. Hanany's group constructs helium balloons that typically float at an altitude of 120,000 feet. NASA launches the balloon payloads from its facilities in Palestine, Texas or Ft. Sumner, New Mexico. Because the Earth's atmosphere emits radiation at the same wavelengths, it is essential to observe the CMB from a balloon platform, above more than 99% of the atmosphere. Liquid helium aboard the payload is used to cool the detectors to a tenth of a degree above absolute zero. This increases their sensitivity. In the lab, students analyze the data collected by the experiment.
Theoreticians in the field use the data collected by experiments to place constraints on various models of the early universe in order to gain a deeper understanding of the specific physics of the Big Bang. Professor Keith Olive studies one of the two major pieces of evidence for the standard Big Bang model (the other being the existence of the cosmic microwave background radiation), the production of the light element isotopes, deuterium, helium, tritium and lithium 7. All elements heavier than lithium are believed to have been formed much later in cosmological history by stellar interiors or supernova explosions. The extraordinary conditions in which these isotopes were formed are known as Big Bang Nucleosythesis (BBN). BBN provides theoreticians with a set of knowable variables that can be plugged into formulae to begin solving the remaining questions of astrophysics. Students in Olive's research group use data from accelerator runs to place strong constraints on the possible properties of dark matter.
Professor Yong-Zhong Qian's research interests are in the area of neutrino astrophysics and nucleosynthesis. Taking advantage of observational progress, Qian has initiated a novel approach to study the origin of the elements involving the study of binary stars, where a small star has a larger companion, and the larger star explodes as a supernova. During this explosion a fraction of the supernova products are directly painted on the surface of the small star. If the explosion does not disrupt the binary, the small star with special chemical enrichment on its surface will have a neutron star or black hole companion that was left behind by the supernova. A search for such binaries can provide opportunities to extract the production template for an individual supernova and help to establish whether the formation of a neutron star or black hole affects the elemental production in an essential way.
The Astrophysics and Cosmology group is widely recognized for its research achievements. In January 2001, for example, Science magazine cited one of the MAXIMA group's discoveries relating to CMB radiation as one of the ten most important breakthroughs of the year 2000.
Astrophysics and Cosmology Faculty
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