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Re: (meteorobs) Lyrid fireball?
> April 15-30: "April Fireballs" -- an annual sparse irregular shower of
> bright meteors some of which reach Earth as meteorites. The radiant is
not
> determined; they come from the region of the ecliptic and equator between
20h
> and 24h (Capricornus, Aquarius, Pegasus, etc.).
The subject of a distinct mid to late April stream of "April Bolides" had
some semi-mythical status in the seventies, but was then put seriously to
doubt. As far as I am aware of, no-one has ever been able to supply firm
statistical data that there is a stream of fireballs active between April
15-30, other than the known Virginid related radiants which however are
active over a much longer period. In some sense, "April Bolides" became a
self-fulfilling prophecy in the early seventies, because allerts were issued
sending more people than usual out in the fields during mid and late April
(in The Netherlands at least, where special campaigns for these fireballs
were organized in the early seventies), resulting of course in more
sightings of bright meteors (being simply a function of more eyes out on the
watch) and every bright meteor appearing in April was bombarded an "April
bolide". A true generic relationship between all these mid-late April
fireball sightings as far as I am aware of has never been made strong
though.
In general, I believe there however indeed is some tendency for more
meteorite droppers in the spring (not just 15-30 April) for the northern
hemisphere. That is a function of the ecliptic being higher in the sky
during the early evening during the spring months. The combined effect of
relatively high altitude of radiants on the ecliptic (meteorite droppers are
of asteroidal origin and usually have their radiant near the ecliptic,
although there are exceptions) and this being in the early evening hours,
which means that the incoming asteroidal debris has to catch up with earth,
resulting in a slow relative speed favouring survival of atmospheric
re-entry, favours more meteorite droppings in the Northern hemisphere spring
late afternoon/evening hours.
- Marco Langbroek
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