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(meteorobs) Re: Whence the Taurids? (was Re: Meteor Activity Outlook for November 8-14, 2002)
Lew,
The Taurids are a separate shower, no doubting that. The problem lies in
the fact that they share a common radiant with the asteroidal material
of the antihelion radiant. There is no practical way to distinguish one
from another as they share similar characteristics. Yes the "r" value is
a bit brighter for the Taurids (2.3 vs. 2.8) but the velocity is similar
to the normal antihelion activity. Once cannot assign all the dim
meteors from this source as antihelions and the bright ones as Taurids.
There would be meteors of all magnitude ranges within both groups.
One would think the material from comet Encke would be less dense and
disintegrate easily and quickly in the Earth's atmosphere. Just the
opposite occurs unless I am seeing mostly antihelion material. Most of
the bright Taurids I have seen are long-lasting and often fragment.
Unless I am way off base, these characteristics more often represent
stony material attributed to asteroids. Perhaps Encke is a stony comet?
Who knows? There is also the possibility comet material behaves
differently at lower velocities and will appear much like the stony or
metallic material from asteroids. To me, the Taurids appear much like
antihelion meteors seen year-round. There just happens to be more of
them in November due to the addition of Encke's material. The problem
lies in the fact that no one organizes a meteor watch to see the Delta
Cancrids or the Sagittarids. If they did they may be surprised to see
the bright activity and occasional fragmenting fireball just like you
see in November.
Since the radiants of the Taurids are indistinguishable, I would suggest
that everyone include all meteors from this source as Taurids. If you
are confident of your shower associations then you may wish to attempt
to classify the Taurids into northern and southern branches. The two
branches are of equal strength at this time but as the month progresses,
the northern branch will begin to dominate.
Therefore the Taurids are a legitimate shower but their rates are
enhanced by the normal antihelion activity. Perhaps in future years I
will give more thought to listing the the antihelion radiant as Taurids
instead of vice versa.
Good topic Lew!
Clear Skies,
Bob Lunsford
Lew Gramer wrote:
> Bob Lunsford, in his invaluable weekly 'Outlook', states:
>
>>We are now starting to see an increase in the antihelion activity as the
>>Earth encounters debris from comet 1P Encke ...
>>Unlike most of the annual showers the antihelion radiant is produced by
>>debris from unknown sources orbiting in a direct motion like the earth ...
>>IMO observers may wish to list these meteors as Taurids or "STA or NTA's"
>>depending on whether the meteors radiant from north or south of the ecliptic.
>
>
> Bob, you have advocated for a number of years, treating the ecliptical
> showers as a single complex, rather than considering them as individual
> showers radiating from different constellations throughout the year. I
> personally think this makes a great deal of sense - for exactly those
> reasons you outline in the second and third paragraphs quoted above.
>
> However, in past years, you've generally acknowledged that the Taurid
> complex represents an exception to this. Again, that is for exactly the
> reason you mention in paragraph one, namely that there IS a parent body
> which has been reliably identified for these two showers - Comet Encke.
>
> (In addition, can't the observational characteristics of the Taurids,
> e.g., their observed rates, calculated 'r' factors, etc., be shown to
> be quite distinct from those of the other "ecliptical showers" that
> cover the whole remainder of the annual meteor calendar?)
>
> I am curious to hear Bob's thoughts, and those of other observers and
> theorists, about this question: In which category SHOULD the Taurids
> be classed - as a shower (and a fairly noticeable one at that!) or as
> essentially glorified Sporadics, part of the general ecliptical locus
> which Bob has labeled the "Antihelion radiant"?
>
> This is pretty topical right now, considering that the broad "peaks"
> of these two showers fall respectively last week (STA) and next (NTA)!
>
> Clear skies all, and thanks for your thoughts!
>
> Lew
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