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Dr. David Asher speaks to the EAAS about the 2004 Perseids


"The possibility of a Perseid outburst peaking at 20:50 UT on August 11th is intriguing. The prediction comes from Esko Lyytinen and Tom van Flandern, one of the groups who successfully foresaw the spectacular Leonid meteor storms of recent years.

Advances in meteor stream modelling in the past couple of decades have proved that the Leonids, Perseids and other streams contain dense, narrow filaments (or trails), and that the location of these trails in space can be mapped out with near-perfect accuracy by evaluating the effect of the planets' gravity over time. So we know for sure that this August, very close to the announced time, the Earth is passing near to the trail of material released from the Perseids' parent comet around its return to the Earth in 1862.

When the Earth goes through a dense region, many particles (solid grains) impact the atmosphere and many meteors appear. There is a crucial difference between the Leonid and Perseid cases. With the former, data on meteor storms in the 19th and 20th centuries allowed the predictions for recent years to be calibrated. No such useful past data exist for the Perseids. So while we know that the Earth will have a near miss to the 1862 trail, the resulting level of meteor activity is rather uncertain.

On the one hand, the Perseids' parent comet is larger than the Leonid parent - more material released, and more meteors visible? On the other hand, the miss distance from the centre of the trail is greater than for the best recent Leonid displays - the density has dropped off, and fewer meteors are visible? It's conceivable we could be lucky and have another chance to observe a real meteor storm. But don't count on this - the best (albeit uncertain) estimates put the meteor activity somewhat lower.

At any rate, much of observational astronomy consists of giving it a shot, and realising that you win some, you lose some (often, the uncertain factor being the weather; this time, the additional uncertainty being the limited data on the Perseid trails). On these grounds, it is well worth observing on the evening of the 11th, as soon as the sky is remotely dark enough. Don't wait for twilight to end, or you may miss the best part!"

To find out where the EAAS are observing the 2004 Perseids, Click Here.


Dr. David Asher Biography

Dr Asher is one of the world's leading experts in Near Earth Objects, currently dividing his time between Armagh and Japan where, at the invitation of the Japan Spaceguard Association, he is working at the Bisei Spaceguard Centre, Japan.

However, in recent years has also worked closely with Robert McNaught of the Australian National University, in predicting so precisely, the Leonid Meteor Storms to within a few minutes.

Dr Asher was born in Edinburgh, and between school and university got a kind of student vacation job with Dr Victor Clube and Professor Bill Napier at the Royal Observatory Edinburgh. It was here that he gained his interest in astronomy.

Later, he did his research degree under Clube, and his D.Phil. thesis was on the Taurid meteor stream. He then went to work with Dr Duncan Steel's near-Earth asteroid programme in Australia, (since closed down by the Australian Government), learnt what a telescope was, (his words!), and got to know Robert McNaught.

It was during his time in Australia that he discovered a number of asteroids, one of which has recently been named (16693) Moseley in honour of Terry Moseley, former President of the Irish Astronomical Association, and good friend of the EAAS.

His current job at Armagh is to work with the Director, Professor Mark Bailey, doing theoretical (computational) studies in solar system dynamics. The research project is about sun grazing and Jupiter grazing objects in particular, such as comets and asteroids.


 

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