Ordinary Meeting, 2002 April 27
Astronomy in the next ten years
Prof. Edmunds opened by welcoming members to his department. It was stated that a number of sources worldwide had recently been in broad agreement when producing lists of key themes in astronomical research for the next decade, and it was this list which would be outlined in the talk. As an example, the speaker suggested that most astrophysicists believed that the major puzzles of cosmology would be resolved within a decade.
The speaker first outlined the progress he anticipated in physics. One of the most significant developments was in particle physics - the discovery of the Higgs boson, for which the LEP experiment at CERN had shown tantalising but inconclusive evidence in 2001. Prof. Edmunds believed that the Large Hadron Collider at CERN would resolve this issue when it commenced operation in 2005, if another experiment had not already done so.
The speaker went on to show an image of gravitational lensing of galaxy cluster Abell 2218. He pointed out that we still have little idea of the nature of the dark matter responsible for this phenomenon, and believed this enigma would be somewhat better understood in a decade. One experiment which might aid this cause is the Boulby particle detector – consisting of a large crystal in a deep mine. The well shielded location allows it to search for previously unidentified particles which penetrate the rock, without interference from cosmic rays.
Moving on to the work of the Sudbury Neutrino Observatory, experiments observing the three flavours of neutrino had recorded anomalies in the relative proportions in solar emission. This was suggestive of neutrino mixing, a theory that neutrinos can change flavour whilst in transit from the Sun. Such behaviour is observed in other fundamental particles, but requires the mixing particles to have mass. Thus there is evidence that neutrinos may have mass, and may therefore play a part in the dark matter problem.
The speaker also believed that the "gravity-waves" which Einstein's general relativity predict binary star systems should radiate would be detected in the next decade using arrangements of masses similar to the Michelson interferometers which supported Einstein's special relativity for light. Prof. Edmunds went on to discuss what astronomers might achieve, pointing out how far astronomy had come in the 1990s, and showed an image of a Gamma Ray Burst as an example. These newly observed phenomena are little understood, but emit such intense gamma radiation that they would sterilise an area of space for many light years around, making life impossible in that region.
Prof. Edmunds showed a galaxy which had been placed at redshift 6.56 by its Hα line. Such a redshift is suggestive of a very newly born galaxy, and the speaker viewed the next decade as an unprecedented opportunity to view the whole of galactic history. To illustrate this further, a cluster of galaxies were shown at redshift 4.1, with the early signs of structure clearly visible.
Moving onto the instrumentation of the next decade, the speaker identified the Gaia satellite as one to watch. This will measure stellar parallaxes from the Lagrange point - a solar orbit which closely follows that of the Earth. It hopes to improve the resolution with which these parallaxes can be determined to 4 microarcseconds, which compares well with the Hipparcos satellite, whose 10 milliarcsecond resolution is currently the best available. To illustrate how fine this resolution is, the speaker pointed out that relativistic aberrations due to the solar gravitational field have to be considered on microarcsecond scales.
Moving onto ground-based telescopes, the speaker anticipated that the square kilometre array would be a vital tool in studying stellar formation processes by probing galaxies up to redshift 3. Computational models have proved unsatisfactory since the density difference between the interstellar medium and stellar material is 22 orders of magnitude and not easily simulated. For example, it is observed that protostars emit jets similar to those seen at the poles of quasars. This phenomenon is therefore seen in two different objects with many orders of magnitude difference in size, yet still it remains unexplained. There are still many proposed designs for the square kilometre array, and construction is not due to commence until 2010.
Prof. Edmunds also keenly awaited data from the Very Large Telescope Interferometer (VLTI), which could achieve sufficient resolution in the infrared to resolve surface features on Betelgeuse. Looking further ahead, he believed the OWL 100 metre instrument might reach fruition in around 15 years, using adaptive optics with a laser guide star to achieve optimum resolution in the visible/infrared.
Finally, the speaker speculated that developments in the search for extrasolar planets might be the most exciting. Such studies to date have produced most surprising results, finding a number of large gas giants in very close orbits to their parent stars. The studies have also found that many planetary systems have very eccentric orbits. This contrasts with our own solar system in which the planetary orbits are near-circular, with the gas giants in the outer regions. Prof. Edmunds concluded that there was much to be done in the next decade.
After much applause, the President added that it was interesting to think how much amateurs might contribute in the future as well. The meeting was adjourned for tea, after which Mr. Jonathan Shanklin was invited to give Sky Notes.