Home      Discussion      Topics      Dictionary      Almanac
Signup       Login
Meteoroid

Meteoroid

Overview
A meteoroid is a sand
Sand
Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...

- to boulder
Boulder
In geology, a boulder is a rock with grain size of usually no less than 256 mm diameter. While a boulder may be small enough to move or roll manually, others are extremely massive....

-sized particle of debris in the Solar System
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...

. The visible path of a meteoroid that enters Earth's
Earth's atmosphere
The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...

 (or another body's) atmosphere
Atmosphere
An atmosphere is a layer of gases that may surround a material body of sufficient mass, and that is held in place by the gravity of the body. An atmosphere may be retained for a longer duration, if the gravity is high and the atmosphere's temperature is low...

 is called a meteor, or colloquially a shooting star or falling star. If a meteoroid reaches the ground and survives impact, then it is called a meteorite
Meteorite
A meteorite is a natural object originating in outer space that survives impact with the Earth's surface. Meteorites can be big or small. Most meteorites derive from small astronomical objects called meteoroids, but they are also sometimes produced by impacts of asteroids...

. Many meteors appearing seconds or minutes apart are called a meteor shower
Meteor shower
A meteor shower is a celestial event in which a number of meteors are observed to radiate from one point in the night sky. These meteors are caused by streams of cosmic debris called meteoroids entering Earth's atmosphere at extremely high speeds on parallel trajectories. Most meteors are smaller...

. The root word meteor comes from the Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...

 meteo¯ros, meaning "high in the air".
Discussion
Ask a question about 'Meteoroid'
Start a new discussion about 'Meteoroid'
Answer questions from other users
Full Discussion Forum
 
Unanswered Questions
Encyclopedia
A meteoroid is a sand
Sand
Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...

- to boulder
Boulder
In geology, a boulder is a rock with grain size of usually no less than 256 mm diameter. While a boulder may be small enough to move or roll manually, others are extremely massive....

-sized particle of debris in the Solar System
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...

. The visible path of a meteoroid that enters Earth's
Earth's atmosphere
The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...

 (or another body's) atmosphere
Atmosphere
An atmosphere is a layer of gases that may surround a material body of sufficient mass, and that is held in place by the gravity of the body. An atmosphere may be retained for a longer duration, if the gravity is high and the atmosphere's temperature is low...

 is called a meteor, or colloquially a shooting star or falling star. If a meteoroid reaches the ground and survives impact, then it is called a meteorite
Meteorite
A meteorite is a natural object originating in outer space that survives impact with the Earth's surface. Meteorites can be big or small. Most meteorites derive from small astronomical objects called meteoroids, but they are also sometimes produced by impacts of asteroids...

. Many meteors appearing seconds or minutes apart are called a meteor shower
Meteor shower
A meteor shower is a celestial event in which a number of meteors are observed to radiate from one point in the night sky. These meteors are caused by streams of cosmic debris called meteoroids entering Earth's atmosphere at extremely high speeds on parallel trajectories. Most meteors are smaller...

. The root word meteor comes from the Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...

 meteo¯ros, meaning "high in the air". The Minor Planet Center
Minor Planet Center
The Minor Planet Center operates at the Smithsonian Astrophysical Observatory , which is part of the Center for Astrophysics along with the Harvard College Observatory ....

 does not use the term "meteoroid".

Meteoroid



the International Astronomical Union
International Astronomical Union
The International Astronomical Union IAU is a collection of professional astronomers, at the Ph.D. level and beyond, active in professional research and education in astronomy...

 officially defines a meteoroid as "a solid object moving in interplanetary space, of a size considerably smaller than an asteroid
Asteroid
Asteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones...

 and considerably larger than an atom". Beech and Steel, writing in Quarterly Journal of the Royal Astronomical Society
Royal Astronomical Society
The Royal Astronomical Society is a learned society that began as the Astronomical Society of London in 1820 to support astronomical research . It became the Royal Astronomical Society in 1831 on receiving its Royal Charter from William IV...

, proposed a new definition where a meteoroid is between 100 µm
Micrometre
A micrometer , is by definition 1×10-6 of a meter .In plain English, it means one-millionth of a meter . Its unit symbol in the International System of Units is μm...

 and 10 m across.
The NEO
Near-Earth object
A near-Earth object is a Solar System object whose orbit brings it into close proximity with the Earth. All NEOs have a perihelion distance less than 1.3 AU. They include a few thousand near-Earth asteroids , near-Earth comets, a number of solar-orbiting spacecraft, and meteoroids large enough to...

 definition includes larger objects, up to 50 m in diameter, in this category. Very small meteoroids are known as micrometeoroid
Micrometeoroid
A micrometeoroid is a tiny meteoroid; a small particle of rock in space, usually weighing less than a gram. A micrometeor or micrometeorite is such a particle that enters the Earth's atmosphere or falls to Earth.-Scientific interest:...

s
(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
Comet
A comet is an icy small Solar System body that, when close enough to the Sun, displays a visible coma and sometimes also a tail. These phenomena are both due to the effects of solar radiation and the solar wind upon the nucleus of the 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, 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). Meteoroids moving through the earth's orbital space at about 20 km/sec.

Meteor

"Meteor" and "Meteors" redirect here. For other uses, see Meteor (disambiguation)
Meteor (disambiguation)
A meteor, commonly called a shooting star and falling star, is the visible trace of a meteoroid as it enters the atmosphere. If it survives impact with the Earth's surface, then it is called a meteorite....

.
See also Hydrometeor.


A meteor is the visible path of a meteoroid that has entered the Earth's atmosphere. Meteors typically occur in the mesosphere
Mesosphere
The mesosphere is the layer of the Earth's atmosphere that is directly above the stratosphere and directly below the thermosphere. In the mesosphere temperature decreases with increasing height. The upper boundary of the mesosphere is the mesopause, which can be the coldest naturally occurring...

, and most range in altitude from 75 km to 100 km. Millions of meteors occur in the Earth's atmosphere every day. Most meteoroids that cause meteors are about the size of a pebble
Pebble
A pebble is a clast of rock with a particle size of 4 to 64 millimetres based on the Krumbein phi scale of sedimentology. Pebbles are generally considered to be larger than granules and smaller than cobbles . A rock made predominantly of pebbles is termed a conglomerate...

. 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. 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
Mean free path
In physics, the mean free path is the average distance covered by a moving particle between successive impacts which modify its direction or energy or other particle properties.-Derivation:...

 (10 cm to several metres) the visibility is due to the atmospheric ram pressure
Ram pressure
In physics, ram pressure is a pressure exerted on a body which is moving through a fluid medium. It causes a strong drag force to be exerted on the body. It is given by:P= \rho v^2...

 (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
Meteor shower
A meteor shower is a celestial event in which a number of meteors are observed to radiate from one point in the night sky. These meteors are caused by streams of cosmic debris called meteoroids entering Earth's atmosphere at extremely high speeds on parallel trajectories. Most meteors are smaller...

, 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 meteoroids producing the meteors have been calculated. All of the orbits passed through the asteroid belt
Asteroid belt
The asteroid belt is the region of the Solar System located roughly between the orbits of the planets Mars and Jupiter. It is occupied by numerous irregularly shaped bodies called asteroids or minor planets...

.

Fireball


A fireball is a brighter-than-usual meteor. The International Astronomical Union
International Astronomical Union
The International Astronomical Union IAU is a collection of professional astronomers, at the Ph.D. level and beyond, active in professional research and education in astronomy...

 defines a fireball as "a meteor brighter than any of the planets" (magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...

 −4 or greater). The International Meteor Organization
International Meteor Organization
The International Meteor Organization was founded in 1988 and has several hundred members. IMO was created in response to an ever-growing need for international cooperation on amateur meteor work...

 (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
Zenith
The zenith is an imaginary point directly "above" a particular location, on the imaginary celestial sphere. "Above" means in the vertical direction opposite to the apparent gravitational force at that location. The opposite direction, i.e...

. 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.

Bolide


Astronomy


The word bolide comes from the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

 βολίς (bolis) http://www.myetymology.com/english/bolide.html 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 term generally applies to fireballs reaching magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...

 −14 or brighter. Astronomers tend to use "bolide" to identify an exceptionally bright fireball, particularly one that explodes (sometimes called a detonating fireball). It may also be used to mean a fireball which creates audible sounds.

Geology


Geologist
Geologist
A geologist is a scientist who studies the solid and liquid matter that constitutes the Earth as well as the processes and history that has shaped it. Geologists usually engage in studying geology. Geologists, studying more of an applied science than a theoretical one, must approach Geology using...

s use the term "bolide" more often than astronomer
Astronomer
An astronomer is a scientist who studies celestial bodies such as planets, stars and galaxies.Historically, astronomy was more concerned with the classification and description of phenomena in the sky, while astrophysics attempted to explain these phenomena and the differences between them using...

s do: in geology it indicates a very large impactor
Impactor
Impactor may refer to:* a large meteoroid, asteroid, comet, or other celestial object which causes an impact event* Impactor , fictional character* Impactor , a craft designed for high velocity landing...

. For example, the USGS
United States Geological Survey
The United States Geological Survey is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, and the natural hazards that threaten it. The organization has four major science disciplines, concerning biology,...

 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".

Superbolide


If the magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...

 of a bolide reaches −17 or brighter it is known as a superbolide.

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. Meteorites are sometimes, but not always, found in association with hypervelocity impact crater
Impact crater
In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...

s; during energetic collisions, the entire impactor may be vaporized, leaving no meteorites.

Tektite



Molten 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 dust


Most 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.

Ionization trails


During the entry of a meteoroid or asteroid into the upper atmosphere, an ionization trail is created, where the molecules in the upper atmosphere are ionized
Ionization
Ionization is the process of converting an atom or molecule into an ion by adding or removing charged particles such as electrons or other ions. This is often confused with dissociation. A substance may dissociate without necessarily producing ions. As an example, the molecules of table sugar...

 by the passage of the meteor. Such ionization trails can last up to 45 minutes at a time. Small, sand-grain sized meteoroids are entering the atmosphere constantly, essentially every few seconds in any given region of the atmosphere,and thus ionization trails can be found in the upper atmosphere more or less continuously. When radio waves are bounced off these trails, it is called meteor burst communications
Meteor burst communications
Meteor burst communications , also referred to as meteor scatter communications, is a radio propagation mode that exploits the ionized trails of meteors during atmospheric entry to establish brief communications paths between radio stations up to apart.-How it works:As the earth moves along its...

.

Meteor radars can measure atmospheric density and winds by measuring the decay rate and Doppler shift of a meteor trail.

Color


The visible light produced by a meteor may take on various hues, depending on the chemical composition of the meteoroid, and its speed through the atmosphere. As layers of the meteoroid are stripped off and ionized, the color of the light emitted may change according to the layering of minerals. Some of the possible colors and the compounds responsible for them are: orange/yellow (sodium); yellow (iron); blue/green (copper); purple (potassium); and red (silicate).

Sound


Any sound generated by a meteor in the upper atmosphere, such as a sonic boom, should not be heard until many seconds after the meteor disappeared. However, in certain instances, for example during the Leonid meteor shower of 2001, several people reported sounds described as "crackling", "swishing", or "hissing" occurring at the same instant as a meteor flare. Similar sounds have also been reported during intense displays of Earth's auroras
Aurora (astronomy)
An aurora is a natural light display in the sky particularly in the high latitude regions, caused by the collision of energetic charged particles with atoms in the high altitude atmosphere...

.

Sound recordings made under controlled conditions in Mongolia in 1998 by a team led by Slaven Garaj, a physicist at the Swiss Federal Institute of Technology
École polytechnique fédérale de Lausanne
The École polytechnique fédérale de Lausanne is one of the two Swiss Federal Institutes of Technology and is located in Lausanne, Switzerland.The school was founded by the Swiss Federal Government with the stated mission to:...

 at Lausanne
Lausanne
Lausanne is a city in Romandy, the French-speaking part of Switzerland, and is the capital of the canton of Vaud. The seat of the district of Lausanne, the city is situated on the shores of Lake Geneva . It faces the French town of Évian-les-Bains, with the Jura mountains to its north-west...

, support the contention that the sounds are real.

How these sounds could be generated, assuming they are in fact real, remains something of a mystery. It has been hypothesized by some scientists at NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

 as that the turbulent ionized wake of a meteor interacts with the magnetic field of the Earth, generating pulses of radio waves. As the trail dissipates, megawatts of electromagnetic energy could be released, with a peak in the power spectrum at audio frequencies
Audio frequency
An audio frequency or audible frequency is characterized as a periodic vibration whose frequency is audible to the average human...

. Physical vibrations induced by the electromagnetic impulses would then be heard if they are powerful enough to make grasses, plants, eyeglass frames, and other conductive materials vibrate. This proposed mechanism, although proven to be plausible by laboratory work, remains unsupported by corresponding measurements in the field.

Frequency of large meteors


The biggest asteroid to hit Earth on any given day is likely to be about 40 centimeters, in a given year about 4 meters, and in a given century about 20 meters. These statistics are obtained by the following:

Over at least the range from 5 centimeters (2 inches) to roughly 300 meters (1,000 feet), the rate at which Earth receives meteors obeys a power-law
Power law
A power law is a special kind of mathematical relationship between two quantities. When the frequency of an event varies as a power of some attribute of that event , the frequency is said to follow a power law. For instance, the number of cities having a certain population size is found to vary...

 distribution as follows:


where N(>D) is the expected number of objects larger than a diameter of D meters to hit Earth in a year. This is based on observations of bright meteors seen from the ground and space, combined with surveys of near Earth asteroids. Above 300 meters in diameter, the predicted rate is somewhat higher, with a two-kilometer asteroid (one million-megaton TNT equivalent) every couple of million years — about 10 times as often as the power-law extrapolation would predict.

Seasonal variation in frequency of fireball sightings


The frequency of fireball sightings increases by about 10-30% during the weeks of vernal equinox
Equinox
An equinox occurs twice a year, when the tilt of the Earth's axis is inclined neither away from nor towards the Sun, the center of the Sun being in the same plane as the Earth's equator...

. Even meteorite
Meteorite
A meteorite is a natural object originating in outer space that survives impact with the Earth's surface. Meteorites can be big or small. Most meteorites derive from small astronomical objects called meteoroids, but they are also sometimes produced by impacts of asteroids...

 falls are more common during the spring season. Although this phenomenon has been known for quite some time, the reason behind the anomaly is not fully understood by scientists. Some researchers attribute this to an intrinsic variation in the meteoroid population along Earth's orbit, with a peak in big fireball-producing debris around spring and early summer. Research is in progress for mapping the orbits of the meteors in order to gain a better understanding of the phenemenon.

Notable meteors


Perhaps the best-known meteor/meteorite fall is the Peekskill Meteorite
Peekskill meteorite
The Peekskill meteorite broke up over the United States on October 9, 1992, an event witnessed by thousands across the East Coast. The meteorite broke up over Kentucky and damaged a parked Chevrolet Malibu in Peekskill, New York on impact. Major cities like Pittsburgh witnessed the bright...

,
filmed on October 9, 1992 by at least 16 independent videographers.

Eyewitness accounts indicate the fireball entry of the Peekskill meteorite started over West Virginia at 23:48 UT (±1 min). The fireball, which traveled in a northeasterly direction had a pronounced greenish color, and attained an estimated peak visual magnitude of −13. During a luminous flight time that exceeded 40 seconds the fireball covered a ground path of some 700 to 800 km.

One meteorite recovered at Peekskill, New York
Peekskill, New York
Peekskill is a city in Westchester County, New York. It is situated on a bay along the east side of the Hudson River, across from Jones Point.This community was known to be an early American industrial center, primarily for its iron plow and stove products...

, for which the event and object gained its name, had a mass of 12.4 kg (27 lb) and was subsequently identified as an H6 monomict breccia meteorite. The video record suggests that the Peekskill meteorite had several companions over a wide area. The companions are unlikely to be recovered in the harsh terrain in the vicinity of Peekskill.

2008 TC3
2008 TC3
thumb|right|300px|Ground path of the meteoroid; red line is the path, terminating where it would have hit the ground; green line is the infrasound detection of the explosion; orange crosshairs show METEOSAT IR fireball location; predicted altitudes are listed; exact path and fireball altitude not...

 was discovered on 6 October 2008 and entered the Earth's atmosphere the next day, striking a remote area of northern Sudan. It was the first time a meteoroid had been observed in space and tracked prior to impacting Earth.

A large fireball was observed in the skies near Bone, Indonesia on October 8, 2009. This was thought to be caused by an asteroid approximately 10 meters in diameter. The fireball contained an estimated energy of 50 kilotons of TNT, or about twice the Nagasaki atomic bomb
Fat Man
"Fat Man" is the codename for the atomic bomb that was detonated over Nagasaki, Japan, by the United States on August 9, 1945. It was the second of the only two nuclear weapons to be used in warfare to date , and its detonation caused the third man-made nuclear explosion. The name also refers more...

. No injuries were reported.

A large bolide was reported on 18 November 2009 over southeastern California, northern Arizona, Utah, Wyoming, Idaho and Colorado. At 12:07 a.m., a security camera at the high altitude W. L. Eccles Observatory (9600 ft above sea level) recorded a movie of the passage of the object to the north. Of particular note in this video is the spherical "ghost" image slightly trailing the main object (this is likely a lens reflection of the intense fireball), and the bright fireball explosion associated with the breakup of a substantial fraction of the object. An object trail can be seen to continue northward after the bright fireball event. The shock from the final breakup triggered seven seismological stations in northern Utah; a timing fit to the seismic data yielded a terminal location of the object at 40.286 N, -113.191 W, altitude 27 km. This is above the Dugway Proving Grounds, a closed Army testing base.

History


Although meteors have been known since ancient times, they were not known to be an astronomical phenomenon until early in the 19th century. Prior to that, they were seen in the West as an atmospheric phenomenon, like lightning, and were not connected with strange stories of rocks falling from the sky. Thomas Jefferson
Thomas Jefferson
Thomas Jefferson was the principal author of the United States Declaration of Independence and the Statute of Virginia for Religious Freedom , the third President of the United States and founder of the University of Virginia...

 wrote "I would more easily believe that (a) Yankee professor would lie than that stones would fall from heaven." He was referring to Yale
YALE
RapidMiner, formerly YALE , is an environment for machine learning, data mining, text mining, predictive analytics, and business analytics. It is used for research, education, training, rapid prototyping, application development, and industrial applications...

 chemistry professor Benjamin Silliman's investigation of an 1807 meteorite that fell in Weston, Connecticut
Weston meteorite
The Weston meteorite is a meteorite which fell to earth above the town of Weston, Connecticut at approximately 6:30 in the morning on December 14, 1807. The meteor fall was widely witnessed and reported in newspaper accounts at the time...

. Silliman believed the meteor had a cosmic origin, but meteors did not attract much attention from astronomers until the spectacular meteor storm of November 1833. People all across the eastern United States saw thousands of meteors, radiating from a single point in the sky. Astute observers noticed that the radiant
Radiant (meteor shower)
The radiant or apparent radiant of a meteor shower is the point in the sky, from which meteors appear to originate. The Perseids, for example, are meteors which appear to come from a point within the constellation of Perseus....

, as the point is now called, moved with the stars, staying in the constellation Leo.

The astronomer Denison Olmsted
Denison Olmsted
Denison Olmsted , U.S. physicist and astronomer, was born at East Hartford, Connecticut. Professor Olmsted is credited with giving birth to meteor science after the 1833 Leonid meteor shower over North America spurred him to study this phenomenon.-Biography:In 1813, he graduated from Yale...

 made an extensive study of this storm, and concluded it had a cosmic origin. After reviewing historical records, Heinrich Wilhelm Matthias Olbers predicted its return in 1867, which drew the attention of other astronomers. Hubert A. Newton's more thorough historical work led to a refined prediction of 1866, which proved to be correct. With Giovanni Schiaparelli
Giovanni Schiaparelli
Giovanni Virginio Schiaparelli was an Italian astronomer and science historian. He studied at the University of Turin and Berlin Observatory. In 1859-1860 he worked in Pulkovo Observatory and then worked for over forty years at Brera Observatory...

's success in connecting the Leonids
Leonids
The Leonids is a prolific meteor shower associated with the comet Tempel-Tuttle. The Leonids get their name from the location of their radiant in the constellation Leo: the meteors appear to radiate from that point in the sky. They tend to peak in November.Earth moves through the meteoroid...

 (as they are now called) with comet Tempel-Tuttle, the cosmic origin of meteors was now firmly established. Still, they remain an atmospheric phenomenon, and retain their name "meteor" from the Greek word for "atmospheric".

Earth moves at about 30 km/s in its orbit. Meteoroids also have significant orbital speeds. The differences in velocities where these orbits intersect combined with the gravitational attraction of Earth result in the velocities observed for meteors.

Gallery



Image:Orionid, pedia.org/wiki/Milky_way Milky Way] and to the right of Venus
Venus
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...

. Zodiacal light
Zodiacal light
Zodiacal light is a faint, roughly triangular, whitish glow seen in the night sky which appears to extend up from the vicinity of the sun along the ecliptic or zodiac. Caused by sunlight scattered by space dust in the zodiacal cloud, it is so faint that either moonlight or light pollution renders...

 is also seen at the image.
Image:Orionid meteor.jpg|Orionid
Orionids
The Orionid meteor shower, usually shortened to the Orionids, is the most prolific meteor shower associated with Halley's Comet. The Orionids are so-called because the point they appear to come from, called the radiant, lies in the constellation Orion. Orionids are an annual meteor shower which...


Image:Orionid meteor1.jpg|Orionid
Orionids
The Orionid meteor shower, usually shortened to the Orionids, is the most prolific meteor shower associated with Halley's Comet. The Orionids are so-called because the point they appear to come from, called the radiant, lies in the constellation Orion. Orionids are an annual meteor shower which...


Image:Two orionids and milky way.jpg|Two Orionids and Milky Way
Milky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...


Image:Multi colored Orionid.jpg|Multi-colored Orionid
Image:Orionids and Orion.jpg|Orionid
Image:Meteor trail.jpg|The brightest meteor, a fireball, leaves a smoky, persistent trail drifting in high-altitude winds, which is seen at the right-hand side of the image left by Orionid
Orionids
The Orionid meteor shower, usually shortened to the Orionids, is the most prolific meteor shower associated with Halley's Comet. The Orionids are so-called because the point they appear to come from, called the radiant, lies in the constellation Orion. Orionids are an annual meteor shower which...

.
Image:Meteoroid meteor meteorite.gif|Animated illustration of differences between a meteoroid, meteor and meteorite
Image:Leonid Meteor.jpg|A photograph of a Leonids
Leonids
The Leonids is a prolific meteor shower associated with the comet Tempel-Tuttle. The Leonids get their name from the location of their radiant in the constellation Leo: the meteors appear to radiate from that point in the sky. They tend to peak in November.Earth moves through the meteoroid...

 meteor showing a meteor, its afterglow, and its wake
Image:Meteor_Bolide.JPG|A fireball seen over the desert of Central Australia. Although this occurred during the Lyrids
Lyrids
The Lyrids are a strong meteor shower lasting from April 16 to April 26 each year. The radiant of the meteor shower is located in the constellation Lyra, peaking at April 22—hence they are also called the Alpha Lyrids or April Lyrids. The source of the meteor shower is the periodic Comet...

, its North-East entry angle indicates it is sporadic.
Image:Looking Down on a Shooting Star.JPG|Looking down from the International Space Station at a meteor as it passes through the atmosphere.

See also

  • American Meteor Society
    American Meteor Society
    The American Meteor Society, Ltd. is a non-profit scientific organization established to encourage and support the research activities of both amateur and professional astronomers who are interested in the field of Meteor Astronomy...

     (AMS)
  • Baetylus
    Baetylus
    Baetylus is a Semitic word denoting a sacred stone, which was supposedly endowed with life. According to ancient sources, these objects of worship were meteorites, which were dedicated to the gods or revered as symbols of the gods themselves...

  • Green fireballs
    Green Fireballs
    Green fireballs are a type of unidentified flying object which have been sighted in the sky since the late 1940s . Early sightings primarily occurred in the southwestern United States, particularly in New Mexico...

  • Hydrometeor
  • Impact crater
    Impact crater
    In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...

  • Impact event
    Impact event
    An impact event is the collision of a large meteorite, asteroid, comet, or other celestial object with the Earth or another planet. Throughout recorded history, hundreds of minor impact events have been reported, with some occurrences causing deaths, injuries, property damage or other significant...

  • International Meteor Organization
    International Meteor Organization
    The International Meteor Organization was founded in 1988 and has several hundred members. IMO was created in response to an ever-growing need for international cooperation on amateur meteor work...

  • Meteorite
    Meteorite
    A meteorite is a natural object originating in outer space that survives impact with the Earth's surface. Meteorites can be big or small. Most meteorites derive from small astronomical objects called meteoroids, but they are also sometimes produced by impacts of asteroids...

  • Near-Earth object
    Near-Earth object
    A near-Earth object is a Solar System object whose orbit brings it into close proximity with the Earth. All NEOs have a perihelion distance less than 1.3 AU. They include a few thousand near-Earth asteroids , near-Earth comets, a number of solar-orbiting spacecraft, and meteoroids large enough to...

  • North American Meteor Network
    North American Meteor Network
    The North American Meteor Network was established in June 1995 as an electronic network of people using the Internet to share an interest in meteors...

  • Perseids
    Perseids
    The Perseids are a prolific meteor shower associated with the comet Swift-Tuttle. The Perseids are so-called because the point from which they appear to come, called the radiant, lies in the constellation Perseus. The name derives in part from the word Perseides , a term found in Greek mythology...

  • Tektite
    Tektite
    Tektites are natural glass rocks up to a few centimeters in size, which most scientists argue were formed by the impact of large meteorites on Earth's surface. Tektites are typically black or olive-green, and their shape varies from rounded to irregular.Tektites are among the "driest" rocks, with...

  • Stratospheric micrometeorites
  • Tollmann's hypothetical bolide
    Tollmann's hypothetical bolide
    Alexander Tollmann's bolide, proposed by Kristan-Tollmann and Tollmann in 1994, is a hypothesis presented by Austrian geologist Alexander Tollmann, suggesting that one or several bolides struck the Earth at 7640 BCE , with a much smaller one at 3150 BCE...


External links