[Prev][Next][Index][Thread]

RE: (meteorobs) Chances of another meteor storm?

> I'm also wondering why there is this 33 year period. I mean,
> the dust trails (ejected 1799, 1833, ... of course every 33th
> year, that's clear) will remain on their position (more or
> less) and to me it seems like earth is going to pass through
> them same likely every year.

One important thing to keep in mind is that the dust is not just sitting there out in space. The particles released by the comet are moving along with it at nearly the same speed (70km/s). Slight variations in the speed cause the dust particles to spread out across to whole cometary orbit over many years. This causes the annual activity each time Earth crosses this orbit.

Somehow, the dust has remained in dense, compact trails in a small window around the comet while in other parts of the orbit the trails have been disturbed. Only when earth crosses a trail in the unpertubed window, a meteorstorm can be expected.

I.P. Williams gives a possible explanation in his article: "The Leonid meteorshower: why are there storms, but no regular annual activity?" (MNRAS1997).

The Leonid are moving very fast when they are close to Earth, they then return into the solar system and slow down. At some point almost all speed is lost (to about 2km/s) and the particles return towards the sun. Williams noticed that the point where they return is very close to the orbit of Uranus. He then looked at the orbital periods of the Leonids (33 years) and Uranus (84 years). It seemed that large parts of the Leonid orbit came under the influence of Uranus. In these parts the trails are messed up, but there also was a small section of the orbit which wasn't influenced. 

Coincidentially this is exactly the section of the orbit where the comet is and so the trails remain compact around the comet. In 2160 the section will be pertubed and the orbit of Tempel-Tuttle will change, probably ending the Leonids completely.

I haven't been able to find any comments, critism, additions or follow-ups to this article so I don't know what the current status of this theory is. To me it sounds reasonable.

Yours,

Daniel



--------------------------------------------------------------------------------
The archive and Web site for our list is at http://www.meteorobs.org
To stop getting all email from the 'meteorobs' lists, use our Webform:
http://www.meteorobs.org/subscribe.html
Follow-Ups: