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Perseids 2009

Perseid Meteor Predictions Spot On

Reports from around the world indicate that this year's annual Perseid meteor shower was the best display since the 1990s. The accuracy of the calculations by Jeremie Vaubaillon (Institute of Celestial Mechanics, Paris and California Institute of Technology) a frequent collaborator with Armagh astronomers, and the American astronomer Thomas van Flandern regarding the times of peak activity and numbers of meteors observed, were confirmed by observations.

The theoretical predictions by Vaubaillon and Van Flandern were based on the gravitational attractions of the major planets on the discrete meteor streams associated with the broad Perseid meteoroid trail, have now been confirmed by observations. Rates of up to 200 meteors per hour were reported in America, the Middle East and in some parts of Europe.

Meteors usually have their sources in comets, and annual meteor showers usually originate from periodic comets. In the inner solar system, each time a periodic comet passes perihelion (closest point to the Sun in its orbit around the Sun) it sheds a discrete trail of dust particles which gradually spreads out along the comet's orbit to form a broad trail. A meteor shower occurs whenever the Earth crosses this trail of particles. The parent comet of the Perseids is comet 109/P Swift-Tuttle which has an orbital period of about 130 years and last reached perihelion in 1992.

During the 1990s, when Swift-Tuttle passed close to the Earth, there was much activity during the annual Perseid (August) shower. Since then the number of meteors arriving has greatly decreased as the comet now leaves the inner solar system before its eventual return in about the year 2122. Vaubaillon's calculations focused on 15 discrete trails emitted by the comet in the years AD 59 to AD 1862 and their peaks of activity (both timings and numbers of meteors) as recorded by observers in over 30 countries were close to his predictions.

FOR FURTHER INFORMATION PLEASE CONTACT: John McFarland at the Armagh Observatory, College Hill, Armagh, BT61 9DG. Tel.: 028-3752-2928; FAX: 028-3752-7174; jmf at sign arm.ac.uk