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Deep Space Dust

A 60-year-old astronomical argument concerning the origin of meteoric dust has been refuelled by research done by Canterbury University's Department of Physics and Astronomy.

Since the 1930s, astrono-mers have puzzled over where meteoric dust comes from. The tiny particles have been suggested as being leftovers from the formation of the solar system; the remains of "evaporated" comets; or originating far outside the solar system in deep space. The latter suggestion has generally been dismissed as unlikely, but the Canterbury work has astronomers thinking again.

Professor Jack Baggaley and his team have been using a computerised radar tracking system to analyse the path of small meteoroids entering high in the Earth's atmosphere [Catch A Falling Star, October 1990]. The system is the most powerful in the world, and the results they have been getting have aroused great interest in the international astronomical community.

Of the 250,000 analysed orbits, a significant proportion have been found to be hyperbolic, with the particles travelling at high speeds from outside the solar system. The dust particles are small -- about 100 microns, or a tenth of a millimetre -- but are considerably larger than most interstellar dust particles revealed by their effects on stellar spectra.

Baggaley says that the results suggest that the particles themselves are in orbit around the galactic centre, along with the stars and our Sun, rather than just drifting in space.