Meteoroids are granular fragments in the solar system, ranging from dust to boulders.Meteoroids enter the earth (or otherplanet）The stage in the path where light is emitted and seen after the atmosphere of 30% is called meteor.Many meteors come from the same direction and appear one after another over a period of timemeteor shower。
Meteoroidsmeteor、MeteoriteThey are all fragments in the universe, but they have different names in different states.In the stage of meteorIon tail、meteoric dustOr make a sound and leave traces of smoke and dust.
Meteoroids are granular in the solar systemfragmentAnd its scale can be as small as sand dust and as large as boulder;The larger ones are called asteroids, and the smaller ones areInterstellar dust。fromInternational Astronomical UnionThe official definition is: solid particles running in interplanetary space are smaller than asteroids but smaller than asteroidsatomOr the molecule is still large.The Royal Astronomical Society of the United Kingdom put forward a clearer new definition: a meteoroid is a solid object with a diameter between 100 microns and 10 meters.Near Earth ObjectsIn terms of classification of near earth objects, larger objects with a diameter of 50 m are included in the definition[1]。
meteor
Meteors are meteoroids or asteroids that enter the earth's atmosphere and emit visible light.For an object larger than the free path in the atmosphere (from 10 cm to several meters), its light emission is from the heat generated by the impact pressure entering the atmosphere (not friction, which is different from the common people's cognition).Because most meteors are only sand to grain sized meteoroids, most of the visible light comes from the energy released by electrons when the evaporated atoms of meteoroids collide with the components in the atmosphere.Meteors are simply visible phenomena rather than meteoroids themselves.
Encyclopedia x Knowledgeable: Illustrated Meteor
fireball
Fireballs are brighter meteors than usual.International Astronomical UnionFireball is defined as a meteor that is brighter than any other planet (it is a star with a magnitude greater than - 4 or brighter).International Meteor OrganizationIt is a group of amateur meteor researchers, and has a more specific definition: fireball is a meteor whose brightness exceeds - 3 when seen at the zenith.This definition corrects the difference caused by the distance between the meteors appearing near the horizon and the observers.For example, when a meteor with a brightness of - 1 appears 5 degrees from the horizon, it can be called a fireball, because when converted to appear at the zenith, the brightness of the meteor will reach - 6[2]。
Fireball
Meteoroid
FireballThe origin of "0" comes from the Greek word "β o λ ∨", which is equivalent to what is now called "missile" or "lightning".International Astronomical UnionThere is no official definition of this phenomenon, and it is generally regarded as a fireball.Geologists pay more attention to this phenomenon than astronomers, because it usually means a strong impact event.For example,USGSThe use of this word to describe the size of a general crater formed by the impact of a warhead "implies that we do not need to know the nature of the impactor... whether it is a rock, a metal asteroid or a frozen comet." Astronomers tend to use fireballs with particularly bright ends or explosive phenomena (sometimes also used for fireballs with a series of explosions).
Meteorite
Meteorites have passed throughEarth's atmosphereThe remnant of an asteroid or meteoroid that has not been destroyed after impact with the ground.Meteoroids sometimes, but not always, canHigh velocity impactRelated impact crater found near;Under the impact of high energy, if the impactor is not completelyvaporizationAnd meteorites will be left behind.
Most meteoroids are enteringatmosphereWill be destroyed, and these wrecks are calledmeteoric dust。Meteor dust can stay in the atmosphere for several months. It is catalyzed by chemical reactions in the upper atmosphere andelectromagnetic radiationThe dispersion of color may affect the earth's climate.
Ion tail
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Meteoroid
When a meteoroid or asteroid enters the upper atmosphere, the molecules in the upper atmosphere encountered by it will be ionized and create an ion tail.These ionized trails can last up to 45 minutes. Small meteoroids, such as grain sized meteoroids, often enter the atmosphere, and will be left more or less continuously in specific areas of the upper atmosphere every few secondsionizationMarks.These traces can reflectradio waves, known as meteor burst communication.Meteor radar canwakereflexair wavesAttenuation rate and Doppler displacement, measuring the density and wind of the atmosphere.
voice
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Meteoroid
When bright meteors fly overhead, many people report hearing the sound.This seems impossible because the speed of sound is relatively slow.Any sound produced by a meteor in the upper atmosphere, such as aSonic boom, should be heard a few seconds after the meteor flies past and disappears.However, in some cases, such as in 2001Leonid meteor shower, when brightFireballAt that time, some people reported hearing sounds like "crackling", "rustling" or "hissing".The strongauroraThere are also reports of similar sounds.Many investigators believe that sound is fictional, and it is the sound effect produced with the appearance of light in the brain.But the continuous report and consistent persistence also cause some other doubts.In 1998SwitzerlandA group led by Slaven Garaj, a physicist at the Federal Research Institute, made a recording in Mongolia under controllable conditions, but supported the argument that sound is true.
Assuming that these sounds are real, it is a bit mysterious how these sounds are caused.It is supposed to be the radio pulse caused by the interaction between the active turbulence of meteor dissociation and the earth's magnetic field.When the wake disappears, megawatt electromagnetic energy is released, and a peak in the energy spectrum appears on the audio frequency.If they are strong enough, thiselectromagnetic pulse It can cause vibration of objects, such as plants, plants, eyeglass frames and other conductors, which may produce sound due to vibration.Although the proposed mechanism has been proved to be gapless in the laboratory, in practice, there is still a lack of direct measurement values to compare and verify.
formation
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Many meteoroids come from debris formed after asteroids collide with each other.Although,cometRemaining after leavingCometary tailSubstances usually formmeteor showerHowever, some members will eventually enter other orbits due to scattering and become scattered meteoroids.Other known sources include the moon and Mars. Some meteorites have been confirmed to come from these celestial bodies, which can be referred toLunar meteoriteandMartian meteorite。
track
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Meteoroids and asteroids follow orbits near the sun, but their orbits are very different.Many meteoroids may becometThe debris left on the track, therefore, has a similar track and converges into a streammeteor shower；There are other meteoroids that are not related to any celestial body and are not related to each other (although their orbits must also be related to the Earth or otherplanetRail rendezvous).afterEarth orbitThe maximum speed of nearby meteoroids is about 42 kilometers (26 miles) per second, while the speed of the Earth in orbit is 29.5 kilometers (18 miles) per second. Therefore, the maximum speed of meteoroids encountered with the Earth is about 72 kilometers (44 miles) per second, but this will only happen in meteoroids traveling against the Earth.About 50% of meteors will collide with the Earth in the daytime (or close to the daytime) and become daytime meteors that are difficult to see. Therefore, most meteors, especially those with low brightness, are observed at night when the sky is low in brightness.Meteors are usually observed between 60 km and 120 km high.Enough meteors have been observed, many by the public, and many by accident, but the meteors and meteorites that followed have been enough to calculate the details of the orbit.All these meteors come fromMain beltNear the asteroid.
Perhaps the most famous meteor or meteorite is the Picki meteorite, which fell on October 9, 1992, and was photographed by at least 16 independent cameras.
The visual observation report of Pike meteor shows that it is a fireball, which started at 23:48 Universal Time (± 1 minute)West VirginiaIt emits green light and sound from the northeast. It is estimated that the maximum brightness reaches - 13 level. The flight time to emit fireball brightness exceeds 40 seconds, and the flight path is between 700 and 800 kilometers.
Because the meteorite weighing 12.4kg (27 pounds) was found in Pikeqi, New York (41.28 degrees north latitude, 81.92 degrees west longitude), this event was called Pikeqi Meteorite, and was later recognized as a breccia meteorite with H6 single-phase debris.The video record shows that there may be several meteorites scattered in the vast barren land near Pikeqi.
Discovery history
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Meteoroid motion curve[4]
In November 2022, the Global Meteor Network, a sky observation camera network, found a rare asteroid meteoroid, and also captured its elegant motion curve.[4]
Related hazards
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Even very small meteoroids can harm spacecraft.withHubble Space TelescopeFor example, there are 572 tinyImpact craterAnd the area to be cut.
The US National Aeronautics and Space Administration (NASA) announced today that the Cassini spacecraft obtained direct evidence for the first time that a small meteoroid broke into pieces and then crashed into Saturn's halo.There are many very fast asteroids in the solar system, and the planets are often hit by them.The size of meteoroids impacting Saturn's rings varies from 1 cm to several meters.Researchers have spent years identifying the tracks left by nine meteoroids in 2005, 2009 and 2012.The observation results from Cassini show that Saturn's rings play an effective role in monitoring various surrounding environments, including the internal structure of Saturn and the orbit of the satellite.For example, a thin but very wide ripple (19000km through the inside of the ring) reflects a collision of a giant meteoroid in 1983[3]。
