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| John K. Webb
BSc PhD Camb
Professor
Department and Research Groups
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Research Interests
Do the laws of Nature change with time?:
I lead the work at UNSW which uses high resolution spectroscopy of quasars to search for variations in the fundamental constants of Nature. Over the past 3 years we have analysed a large amount of data taken using the Keck telescope and find a statistically significant effect in the data which is consistent with time variation of the electromagnetic coupling constant (or fine-structure constant), alpha.
The high redshift deuterium abundance and the baryonic density parameter:
One of the great successes of the Big Bang theory is that Big Bang Nucleosynthesis (BBN) calculations predict relative abundances of the light elements (such as Helium, Lithium, Deuterium) which agree well with observations. In principle measurements of Deuterium provide extremely powerful constraints because the the predicted BBN yield is highly sensitive to the cosmological density of baryons. So, if we can measure the primordial relative abundance of Deuterium, we have a precise measurement of the density of the universe. The latter is very important in cosmology because we need to know all the contributions to the total energy density of the universe in order to fully understand its past and future expansion history.
Extra-solar planets:
"Our department has a wide-field imaging telescope at Siding Spring, NSW, the Automated Patrol Telescope (APT). The facility was developed and is maintained by Michael Ashley and is currently being used to search for extra-solar planets, using the transit method. The idea is simple: monitor the apparent brightnesses of a large sample of stars. Some of those stars will have planets whose orbital planes align to Earth, so that a small reduction in the star's brightness is seen when the planet eclipses it's host star.
We eagerly await the delivery of a new CCD camera being built at the Anglo-Australian Observatory (expected early in 2006) which will increase our observing effeciency by about an order of magnitude."
Selected Publications
- Limits on Variations in Fundamental Constants from 21-cm and Ultraviolet Quasar Absorption Lines, Tzanavaris, P.; Webb, J. K.; Murphy, M. T.; Flambaum, V. V.; Curran, S. J. Physical Review Letters, vol. 95, Issue 4, (2005)
- The University of New South Wales Extrasolar Planet Search: methods and first results from a field centred on NGC 6633, Hidas, M. G.; Ashley, M. C. B.; Webb, J. K.; Irwin, M.; Phillips, A.; Toyozumi, H.; Derekas, Christiansen, J. L.; Nutto, C.; Crothers, S. Monthly Notices of the Royal Astronomical Society, Volume 360, Issue 2, (2005) 703-717
- Deuterium/hydrogen in a new Lyman limit absorption system at z= 3.256 towards PKS1937-1009, Crighton, N. H. M.; Webb, J. K.; Ortiz-Gil, A.; Fernández-Soto, A. Monthly Notices of the Royal Astronomical Society, Volume 355, Issue 4, (2004) 1042-1052
- Cosmological evolution of heavy-element and H2 abundances, Curran, S. J.; Webb, J. K.; Murphy, M. T.; Carswell, R. F. Monthly Notices of the Royal Astronomical Society, Volume 351, Issue 1, (2004) L24-L28
- Cosmological variation of the deuteron binding energy, strong interaction, and quark masses from big bang nucleosynthesis, Dmitriev, V. F.; Flambaum, V. V.; Webb, J. K. Physical Review D, vol. 69, Issue 6, (2004)
- Further evidence for a variable fine-structure constant from Keck/HIRES QSO absorption spectra, Murphy, M. T.; Webb, J. K.; Flambaum, V. Monthly Notices of the Royal Astronomical Society, Volume 345, Issue 2, (2003) 609-638
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A catalogue of damped Lyman alpha absorption systems and radio flux densities of the background quasars, S. J. Curran (UNSW), J. K. Webb (UNSW), M. T. Murphy (UNSW),R. Bandiera (Arcetri), E. Corbelli (Arcetri),V. V. Flambaum (UNSW) Comments: 26 Pages, 12 PS tables, 1 embedded table. Accepted by PASA. Continuously updated online catalogue available at
http://www.phys.unsw.edu.au/~sjc/dla/
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The Gaseous Extent of Galaxies and the Origin of Lya Absorption Systems. V. Optical and Near-Infrared Photometry of Lya-absorbing Galaxies at z < 1, Hsiao-Wen Chen (Carnegie Observatories), Kenneth M. Lanzetta (SUNY at Stony Brook), John K. Webb (UNSW), Xavier Barcons (Universidad de Cantabria) Astrophys.J. 559 (2001) 654-674
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Could We Detect Molecular Oxygen in the Atmosphere of a Transiting Extra-Solar Earth-Like Planet? John K. Webb(UNSW), Imma Wormleaton(UNSW) Astron. Soc. Austr, 2001, 18, 252-258
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Further Evidence for Cosmological Evolution of the Fine Structure Constant, J.K. Webb, M.T. Murphy, V.V. Flambaum, V.A. Dzuba, J.D. Barrow, C.W. Churchill, J.X. Prochaska, A.M. Wolfe Phys.Rev.Lett. 87 (2001) 091301
Contact Details
Mail Address
School of Physics
The University of New South Wales
SYDNEY 2052
Australia
Email Address
Phone Number
Facsimile Number
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