chip@vaxwaller.UUCP (Chip Kozy) (09/20/85)
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Yesterday, Sept 19, at about 10:37 PM north-central California
was shown some of mother natures own pyrotechnics. Luckily I was in
a position to witness this phenomina.
At approximately 10:37 PM i noticed what looked like some
of those not-too-spectacular sky rockets that a lot of people seem
to have around the 4th of July. As I watched, though, I realized
that this was something different. The description of what I saw follows:
At a latitude roughly the same as San Francisco, and about 30
miles East of SF, the object was first sighted due North of the town
of Martinez, Cal. The object was about 35-40 degrees above the horizon,
travelling roughly SE. Trajectory appeared to be flat (parallel to the
horizon), with the object moving relatively slowly. The "head" of this
thing was white and trailed what appeared to be "sparks" (as opposed to
the usual "tail" I've seen in other meteors), with chunks breaking off
and curving downward to disappear shortly thereafter (the pieces that
broke off were also white at the "head"). The "sparks" ranged from
a yellowish-orange to reddish-orange, and, behind the main "head",
trailed about three finger widths (maybe a bit more...I was stopped
in the middle of the street on my motorcycle at this time, and was
trying to watch the thing and watch for traffic at the same time).
The main body continued on, and I lost sight of it behind a building
(funny, didn't SEEM that low :-)). During its' "flight" it shed
about six pieces. Toward the end of my view of it, it seemed to
stop coming apart at the seams...as if it had skipped out of the
heavier atmosphere. Total viewing time was about 15-20 seconds
(estimated due to the realtive inaccessability of my watch beneath
two layers of leather). One funny effect was that while watching it,
a plane crossed its' path...plane was high enough to not be heard,
but the running lights were clearly seen...and the thing went behind
the plane. (Would have loved to have my camera about then.)
Anyway, that's my experience. I do have a couple of questions.
1. Can any conclusion be drawn from the above observation as to
A. composition
B. size
2. Does this sound like a meteor(ite), or more like a piece
of space junk comitting suicide?
3. Is this one of the more rare sightings (as opposed to the
sightings during the various "meteor showers" throughout
the year)?
Anyway, I thank you for putting up with a neophite like myself,
and any info you can give me regarding the above would be greatly
appreciated.
Happiness;
Chip
--
Chip Kozy (415) 939-2400 x-2048
Varian Inst. Grp. 2700 Mitchell Dr.
Walnut Creek, Calif. 94598
{zehntel,amd,fortune,resonex,rtech}!varian!chipsas@wuphys.UUCP (Scott A. Sandford) (09/30/85)
This is the first time I've tried posting to
the net so please bear with me if I make a mess of
this.
I'm responding to Chip concerning the fireball
he saw over California. In answer to your questions:
(1) It's really tough to determine the composition
and size of a meteor simply from visual observations.
More sopisticated spectral techniques can determine the
basic elements present by looking for the various
emission lines of the excited atoms in the ion trail.
This has been done in the past and it was found that
the majority of meteors in the sky have elemental
abundances that are "chondritic", that is they have
elemental abundaces that are similar to those seen in
the most common meteorites we find on the earth. These
meteorites are made up predominantly of silicate
minerals and contain mostly Si, Fe, S, Ni, Mg, Al, Ca, Mn, and
Cr with a lot of other elements in minor amounts.
The size is also difficult to tell accurately, but
from your account it is certain that it was reasonably
large as meteoroids go. A first guess would be larger
than a softball but smaller than a football field (or
the resulting collision with earth would have been a
serious problem for the local inhabitants).
(2) Again, from your discription it could have been
either space junk or a real meteoroid. The amount of
trash in orbit is increasing at a rapid pace and
man-made meteors are increasing correspondingly.
Spectroscopic examination of the ion trail would be
a good way to seperate the two types of events.
(3) Yes, the fireball you saw was a special event!
I have been in the meteorite field for some time, have
gone to Antarctica as part of a meteorite collection
expedition (on which we found almost 300 meteorite
fragments), and have worked on the cosmic dust
collected by NASA in the stratosphere, but I've never
seen a fireball. Consider yourself to be a lucky dog!
The normal meteors you see during meteor showers
are due to small meteoroids that are no larger than
grains of sand. The showers are associated with comets
and the dust grains are thought to be very fragile.
The resulting tracks are, thus, relatively dim compared
to the tracks produced by fireballs. Fireballs,
however, produce a bright trail that can be seen for
some time. Due to the large size and high velocity of
fireball producing objects, these bodies experience
very large aerodynamic pressures during atmospheric
entry. This usually results in the fragmentation of
the meteoroid, leadin to the "sparks" you saw. These
are fragments leaving the main mass. The pressure
often shatters the meteoroid entirely and the result is
a "shower" of marble to fist-sized stones that fall
over a large area (typically 5 x 10 miles) of the earth
called a "strewn field."
I hope this has answered your questions. I fear
it may be a bit chaotic (my spectrometer called me away
several times during my babbling here) so if you have
additional questions, feel free to ask again!
CHOW
>
> Yesterday, Sept 19, at about 10:37 PM north-central California
> was shown some of mother natures own pyrotechnics. Luckily I was in
> a position to witness this phenomina.
>
> At approximately 10:37 PM i noticed what looked like some
> of those not-too-spectacular sky rockets that a lot of people seem
> to have around the 4th of July. As I watched, though, I realized
> that this was something different. The description of what I saw follows:
>
> At a latitude roughly the same as San Francisco, and about 30
> miles East of SF, the object was first sighted due North of the town
> of Martinez, Cal. The object was about 35-40 degrees above the horizon,
> travelling roughly SE. Trajectory appeared to be flat (parallel to the
> horizon), with the object moving relatively slowly. The "head" of this
> thing was white and trailed what appeared to be "sparks" (as opposed to
> the usual "tail" I've seen in other meteors), with chunks breaking off
> and curving downward to disappear shortly thereafter (the pieces that
> broke off were also white at the "head"). The "sparks" ranged from
> a yellowish-orange to reddish-orange, and, behind the main "head",
> trailed about three finger widths (maybe a bit more...I was stopped
> in the middle of the street on my motorcycle at this time, and was
> trying to watch the thing and watch for traffic at the same time).
> The main body continued on, and I lost sight of it behind a building
> (funny, didn't SEEM that low :-)). During its' "flight" it shed
> about six pieces. Toward the end of my view of it, it seemed to
> stop coming apart at the seams...as if it had skipped out of the
> heavier atmosphere. Total viewing time was about 15-20 seconds
> (estimated due to the realtive inaccessability of my watch beneath
> two layers of leather). One funny effect was that while watching it,
> a plane crossed its' path...plane was high enough to not be heard,
> but the running lights were clearly seen...and the thing went behind
> the plane. (Would have loved to have my camera about then.)
>
> Anyway, that's my experience. I do have a couple of questions.
>
> 1. Can any conclusion be drawn from the above observation as to
> A. composition
> B. size
>
> 2. Does this sound like a meteor(ite), or more like a piece
> of space junk comitting suicide?
>
> 3. Is this one of the more rare sightings (as opposed to the
> sightings during the various "meteor showers" throughout
> the year)?
>
> Anyway, I thank you for putting up with a neophite like myself,
> and any info you can give me regarding the above would be greatly
> appreciated.
>
> Happiness;
> Chip
>
> --
>
>
> Chip Kozy (415) 939-2400 x-2048
> Varian Inst. Grp. 2700 Mitchell Dr.
> Walnut Creek, Calif. 94598
> {zehntel,amd,fortune,resonex,rtech}!varian!chip
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