(meteorobs) Fireballs

[Marco Langbroek]

Op 24-2-2010 09:42, Stuart Saunders schreef:
> Robert, you say "February is the start of the fireball season, when an
> abundance of fireballs seem to occur. This lasts well into April and
> seems to occur mostly during the early evening hours."
>
> I am wondering are these from one or a few radiants, or are they
> random? What might cause random fireballs in a particular season, and
> in the evening - contrary to earths motion, etc?
>
> I would be grateful for any thoughts.
>
> Stuart.

During this period, the highest part (in declination) of the ecliptic, in the 
northern hemisphere, is high in the sky in the late afternoon and early evening.

This means that activity from ecliptic sources (sporadic asteroidal origin 
meteoroids) are favoured as their source area is relatively high in the sky.
These are objects in prograde orbits with similar speeds to the earth - their 
radiants will tend to cluster near the opposit side of where the earth is moving 
to. This point is higher in the sky in northern hemisphere spring evening. By 
contrast, retrograde, sporadic cometary origin meteoroids will tend to have 
their radiant clustered near the point where the earth is moving to. Their 
activity will be highest in northern hemisphere autumn mornings.

Asteroidal meteoroids tend to be relatively big and solid relative to cometary 
meteoroids (they are the potential meteorite producers). Hence their fireball 
potential. In spring, the asteroidal sporadic source is hence more active 
(favourable radiant area position in the evening sky) and they are relatively 
large. Together, this means: good fireball activity. But don't let this fool 
you. You need to observe a lot of spring hours to capture them.

- Marco

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Dr Marco (asteroid 183294) Langbroek
Dutch Meteor Society (DMS)

e-mail: dms at marcolangbroek.nl
http://www.dmsweb.org
http://www.marcolangbroek.nl
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