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Дата изменения: Tue Dec 14 13:44:25 1999
Дата индексирования: Tue Oct 2 03:29:57 2012
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Поисковые слова: crab nebula

W.M. Napier, Senior Research Fellow

Dr Bill Napier continued his research into the origin and evolution of interplanetary dust, the effects of dust and small-body impacts on the Earth, and the analysis of extragalactic redshifts.

1.

A variable zodiacal cloud model was developed in order to investigate the variable accretion rate of extraterrestrial dust on the Earth. The model considers a population of comets, injected at random into short-period, Earth crossing orbits, where they disintegrate, producing dust. The dust particles so produced undergo mutual collisions as well as spiralling into the Sun under the influence of radiation pressure. Preliminary results show that large fluctuations in the dust population are likely to result.

2.

An analysis of the recession velocities of nearby galaxies (103 with velocities less than 500km s^-1, out to a distance of $\sim$10Mpc) was carried out with a view to checking whether a redshift periodicity of 37.5km s^-1 exists in this dataset, as had been found in other extragalactic datasets. The new analysis yielded a local cosmological expansion of $62\pm 5$km s^-1 Mpc^-1, closely similar to the corresponding values $64\pm6$ and $63\pm4$ found by the two groups studying Type Ia supernovae. However, the most significant (and extraordinary) result to emerge from this study was the confirmation that there is indeed a periodicity of 37.5km s^-1 in the recession velocity of these nearby galaxies, a result previously found by Napier and a co-author in a more accurate dataset extending to 2600km s^-1.

3.

Reviews of the small-body impact hazard, and the dust hazard, on timescales relevant to civilization, were prepared and published.

4.

Miscellaneous activities: student supervision at various levels (e.g. two QUB undergraduates, one school work experience student), and acting as external examiner to a Ph.D. student at the University of Wales at Cardiff. The alleged meteorite crater near Belleek was investigated early in the year with Mark Bailey and Tom Mason and shown not to be meteoritic.

5.

PUS: five presentations were made, ranging from IAU Symposium 194 (Armenia) to colloquia and popular talks. In addition, a popular review (`Comets, Dragons and Prophets of Doom') was published in the PPARC journal Frontiers, and a novel (`Nemesis'), a thriller with a science base exploring the issue of the asteroid impact hazard to civilization, was written and published by Hodder Headline plc. These outreach activities resulted in wide media coverage, including interviews for television documentaries, full-page reports in the national press as well as interviews on national BBC radio. The book `Nemesis' has currently sold more than 15,000 hardback copies. The PPARC-funded STEM course on scientists and the media was found to provide a useful introduction to dealing with the various mass media.