[meteorite-list] Meteorites 101

From: Jonathan E. Dongell <jdongell_at_meteoritecentral.com>
Date: Sun, 16 Jan 2011 14:18:02 -0800
Message-ID: <00a001cbb5cb$3d8cd760$6401a8c0_at_homepc>

Barrett,
So is the "Asteroid Belt" actually;
a "Meteriod Belt", an "Asteriod Belt", or a "Satellite Belt" ? ;~}
Jonathan



----- Original Message -----
From: "Barrett" <BarrettWF at comcast.net>
To: <Meteorite-list at meteoritecentral.com>
Sent: Saturday, January 15, 2011 5:29 PM
Subject: [meteorite-list] Meteorites 101


>
> The definitive source WIKIPEDIA!! Says;
>
> MeteoroidThe current official definition of a meteoroid from the
> International Astronomical Union is "a solid object moving in
> interplanetary space, of a size considerably smaller than an asteroid and
> considerably larger than an atom".[1][2] Beech and Steel, writing in
> Quarterly Journal of the Royal Astronomical Society, proposed a new
> definition where a meteoroid is between 100 ?m and 10 m across.[3] The NEO
> definition includes larger objects, up to 50 m in diameter, in this
> category. Very small meteoroids are known as micrometeoroids (see also
> interplanetary dust).
>
> The composition of meteoroids can be determined as they pass through
> Earth's atmosphere from their trajectories and the light spectra of the
> resulting meteor. Their effects on radio signals also give information,
> especially useful for daytime meteors which are otherwise very difficult
> to observe. From these trajectory measurements, meteoroids have been found
> to have many different orbits, some clustering in streams (see Meteor
> showers) often associated with a parent comet, others apparently sporadic.
> Debris from meteoroid streams may eventually be scattered into other
> orbits. The light spectra, combined with trajectory and light curve
> measurements, have yielded various compositions and densities, ranging
> from fragile snowball-like objects with density about a quarter that of
> ice,[4] to nickel-iron rich dense rocks.
>
> Meteoroids travel around the Sun in a variety of orbits and at various
> velocities. The fastest ones move at about 26 miles per second (42
> kilometers per second) through space in the vicinity of Earth's orbit. The
> Earth travels at about 18 miles per second (29 kilometers per second).
> Thus, when meteoroids meet the Earth's atmosphere head-on (which would
> only occur if the meteors were in a retrograde orbit), the combined speed
> may reach about 44 miles per second (71 kilometers per second).
>
> Meteor"Meteor" and "Meteors" redirect here. For other uses, see Meteor
> (disambiguation).
> See also Hydrometeor.
>
> Comet 17P/Holmes and GeminidA meteor is the visible path of a meteoroid
> that has entered the Earth's atmosphere. Meteors typically occur in the
> mesosphere, and most range in altitude from 75 km to 100 km.[5] Millions
> of meteors occur in the Earth's atmosphere every day. Most meteoroids that
> cause meteors are about the size of a pebble. They become visible between
> about 40 and 75 miles (65 and 120 kilometers) above the Earth. They
> disintegrate at altitudes of 30 to 60 miles (50 to 95 kilometers). Meteors
> have roughly a fifty percent chance of a daylight (or near daylight)
> collision with the Earth as the Earth orbits in the direction of roughly
> west at noon.[clarification needed] Most meteors are, however, observed at
> night as low light conditions allow fainter meteors to be observed.
>
> For bodies with a size scale larger than the atmospheric mean free path
> (10 cm to several metres)[clarification needed] the visibility is due to
> the atmospheric ram pressure (not friction) that heats the meteoroid so
> that it glows and creates a shining trail of gases and melted meteoroid
> particles. The gases include vaporized meteoroid material and atmospheric
> gases that heat up when the meteoroid passes through the atmosphere. Most
> meteors glow for about a second. A relatively small percentage of
> meteoroids hit the Earth's atmosphere and then pass out again: these are
> termed Earth-grazing fireballs (for example The Great Daylight 1972
> Fireball).
>
> Meteors may occur in showers, which arise when the Earth passes through a
> trail of debris left by a comet, or as "random" or "sporadic" meteors, not
> associated with a specific single cause. A number of specific meteors have
> been observed, largely by members of the public and largely by accident,
> but with enough detail that orbits of the incoming meteors or meteorites
> have been calculated. All of them came from orbits from the vicinity of
> the asteroid belt.[6]
>
> FireballA fireball is a brighter-than-usual meteor. The International
> Astronomical Union defines a fireball as "a meteor brighter than any of
> the planets" (magnitude -4 or greater).[7] The International Meteor
> Organization (an amateur organization that studies meteors) has a more
> rigid definition. It defines a fireball as a meteor that would have a
> magnitude of -3 or brighter if seen at zenith. This definition corrects
> for the greater distance between an observer and a meteor near the
> horizon. For example, a meteor of magnitude -1 at 5 degrees above the
> horizon would be classified as a fireball because if the observer had been
> directly below the meteor it would have appeared as magnitude -6.[8]
>
> Bolide
> An especially bright meteor, a bolide (in astronomy)"Bolide" redirects
> here. For the Swedish guided missile BOLIDE, see RBS 70.
> In astronomy
> The word bolide comes from the Greek ????? (bolis) which can mean a
> missile or to flash. The IAU has no official definition of "bolide", and
> generally considers the term synonymous with "fireball". The bolide term
> is generally used for fireballs reaching magnitude -14 or brighter.[9]
> Astronomers tend to use the term to mean an exceptionally bright fireball,
> particularly one that explodes (sometimes called a detonating fireball).
>
> In geology
> Geologists use the term "bolide" more often than astronomers do: in
> geology it indicates a very large impactor. For example, the USGS uses the
> term to mean a generic large crater-forming projectile "to imply that we
> do not know the precise nature of the impacting body ... whether it is a
> rocky or metallic asteroid, or an icy comet, for example".[10]
>
> SuperbolideIf the magnitude of a bolide reaches -17 or brighter it is
> known as a superbolide.[9][11]
>
> MeteoriteMain article: meteorite
> A meteorite is a portion of a meteoroid or asteroid that survives its
> passage through the atmosphere and impact with the ground without being
> destroyed.[12] Meteorites are sometimes, but not always, found in
> association with hypervelocity impact craters; during energetic
> collisions, the entire impactor may be vaporized, leaving no meteorites.
>
> TektiteMain article: tektite
>
> Two tektitesMolten terrestrial material "splashed" from a meteorite impact
> crater can cool and solidify into an object known as a tektite. These are
> often mistaken for meteorites.
>
> Meteoric dustMost meteoroids burn up when they enter the atmosphere. The
> left-over debris is called meteoric dust or just meteor dust. Meteor dust
> particles can persist in the atmosphere for up to several months. These
> particles might affect climate, both by scattering electromagnetic
> radiation and by catalyzing chemical reactions in the upper
> atmosphere.[13]
>
> Does this help any? Seems about correct.
> -Barrett
>
> -----Original Message-----
> From: meteorite-list-bounces at meteoritecentral.com
> [mailto:meteorite-list-bounces at meteoritecentral.com] On Behalf Of
> GeoZay at aol.com
> Sent: Saturday, January 15, 2011 5:59 PM
> To: meteorite-list at meteoritecentral.com
> Subject: Re: [meteorite-list] Meteorites 101
>
>
>>>Bolide is a term that it's good to avoid. It doesn't mean anything... or
> rather, it means too many different things. "Fireball" unambiguously
> means
> a
> meteor of a specific apparent brightness. "Bolide" is simply confusing.<<
>
>
>
> I usually think of a fireball as a meteor with a magnitude brighter than
> -3. I also sometimes think of a Bolide as being a fireball that has
> produced
> a sonic boom as well.
> GeoZay
>
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Received on Sun 16 Jan 2011 05:18:02 PM PST