(meteorobs) showers shifting through time

Marco Langbroek marco.langbroek at online.nl
Fri Oct 11 09:34:37 EDT 2013

Op 11-10-2013 12:30, Anne van Weerden schreef:
> Hi Carlos,
>   From a relativistic point of view, orbits which are very elongated
> should have more shift, due to their perihelion precession, than more
> circular ones.
> But I guess there are also other influences such as gravity of the large
> planets, I do not know much about the precise orbits of showers.
> Greetings, Anne

While this is a factor, the major factor causing a shift to a later time over 
time is not related to the meteoroid stream orbit at all, but simply the result 
of the precession of the equinoxes. Which is around 1 degree per 71 year.

So it are not the shower orbits that shift: it is our calendrical system that 
shifts along with the vernal equinox, due to precession, a gentle wobble of the 
Earth axis itself.

Of course, there is a true shift for streams as well caused by gravitational 
perturbance of the orbit. But the main cause of the average 1 day shift per 71 
years is precession of the vernal equinox.

- Marco

> On 11/10/2013 03:53, Trenary, Carlos wrote:
>> Long ago I was taught that the Leonid meteor shower shifts in time and
>> occurs about one day later for every 71 years that passes. But is it
>> correct that not all showers gradually shift according to such a
>> pattern? Do all showers occur at the same time according to the tropical
>> year, or do some have a different rate of shift?
>> Carlos Trenary
>> Carlos.trenary at vanderbilt.edu <mailto:Carlos.trenary at vanderbilt.edu>
>> Carlos.trenary at gmail.com <mailto:Carlos.trenary at gmail.com>
>> Nashville Tennessee, USA
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