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Re: (meteorobs) QUADRANTID excerpt from "CCNet 7/2002 - 10 January 2002"


Dear All,

Rob is quite right that refering to radiant and orbits is tautological. I guess 
I did in order to make some distinction between what we observed (radiants and 
velocity) and what is derived of it (orbits), and for the benefit of CCNet 
readers who might not know that radiant structure also means structuring in 
orbits (indeed, that radiant position and velocity determine the orbit you 
derive from them). Although that now seems to have reached the opposite... 
Maybe I should have written it as radiants/orbits to more accurately reflect 
that they are intertwined.

- Marco


Quoten Rob McNaught <rmn@aaocbn.aaodot gov.AU>:

> > Moreover, the data are structured: they show
> > a number of interesting correlations between velocity and mass on the one
> > hand, and radiant structure and orbital elements on the other hand.
> 
> My comment here is not meant to have any bearing on the age of the
> Quadrantids or their progenitor, or the content of the original paper
> that Marco refers to (which I have not read).  Just pointing out a tautology
> in the above sentence.  A radiant (sky coordinates, speed, time and
> location of the meteor in the atmosphere) is merely another way of
> expressing an orbit.  It is identical to the three Cartesian heliocentric
> coordinates and heliocentric velocity vector plus time or the more
> familiar angular "orbital elements".  As the three are formally
> equivalent, there must always be a formal and exact relationship between
> radiant structure and orbital elements.  Saying the radiant is structured
> means the orbital elements are structured.  I'd doubt that this pedantry
> detracts in any way from the point Marco is making, but I suspect this is a
> popular misconception.
> 
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