Meteors are nice
From MariachiWiki
Group 3
Definitions
Meteor
According to the International Meteor Organization,a meteor is "the light phenomenon which results from the entry into the Earth's atmosphere of a solid particle from space." These meteors are classified into different categories, based upon their sizes and composition. These different sizes determine names of the meteors and the different compositions tell you the composition of the meteor.
A meteor is the visible event that occurs when a meteoroid or asteroid enters the earth's atmosphere and becomes brightly visible. The visibility is due to the heat produced by the ram pressure of atmospheric entry.
Ram Pressure
Pressure exerted on a body which is moving through a fluid medium. It causes a strong drag force to be exerted on the body. When a meteor is traveling through the Earth's atmosphere the ram pressure heats the air which in turn heats the meteoroid as it flows around it.
Meteoroid
A small sand to boulder-sized particle of debris in the Solar system. According to the International Astronomical Union a meteoroid is a solid object moving in interplanetary space, of a size considerably smaller than an asteroid and considerably larger than an atom or molecule.
Fireball
A very bright meteor.
Bolide
A term used by geologists to descibe a "very large impactor" or an "exceptionally bright fireball" that explodes. Very similar to a fireball.
Meteorite
A portion of a meteoroid or asteroid that survives its passage through the atmosphere and impact with the ground without being destroyed. Associated with hypervelocity impact craters.
Tektite
Molten material that is "splashed" from a crater and cooled. Often mistaken as meteorites.
Interesting Questions
What methods or techniques are used to determine the ionized trail from meteors?
When a meteorite is travelling through the atmopshere, it heats the surrounding atoms and ionizes them. This creates an ion-trail in the atmosphere. If we send a radar pulse from the ground, it will be reflected from these trails of ions, and we can tell there was a meteorite there.
How is the technology used to detect cosmic rays similar to that used to detect the ionized path of meteors?
Both technologies are pretty much one and the same. To detect cosmic rays, a new method considered by many groups (including MARIACHI) is to use radio waves to bounce off the trails of the particles created through cosmic ray showers. These radio waves would also bounce off the ionized trail of meteors. The way that we can differentiate between the two groups is by determining the amount of time the signal is reflected for.
What is forward and back scattering?
Forward scattering is when a radio wave is deflected off the ionized trail of a meteor by a radio station to a reciever that is a large distance away from it. Forward scattering is primarily used to gain data on general meteor activity. According to The International Meteor Organization, A lower VHF radio receiver (30-100 MHz) is located at a large distance (about 500-2000 km) from a transmitter at the same frequency. Direct radio contact is impossible due to the curvature of the Earth. When a meteor enters the atmosphere, its trail may reflect the radio waves from the transmitter to the receiver. At the receiver, where the signal of the transmitter is normally not received, the transmission can then be received for a moment, as long as the meteor trail is present. Such reflections can last from a tenth of a second to a few minutes. The received signal characteristics are related to physical parameters of the meteoric event.
Back scattering is radio wave propagation in which the direction of the incident and scattered waves, resolved along a reference direction (usually horizontal), are oppositely directed.
What is the effect of a meteor's size on its detectability?
Why do meteors glow?
Observers often call meteors shooting stars or falling stars because they look like stars falling from the sky. People sometimes call the brightest meteors fireballs. A meteor appears when a particle or chunk of metallic or stony matter called a meteoroid enters the earth's atmosphere from outer space. Air friction 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.
Most meteoroids disintegrate before reaching the earth. But some leave a trail that lasts several minutes. Meteoroids that reach the earth are called meteorites.
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).
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). The earth travels at about 18 miles per second (29 kilometers per second). Thus, when meteoroids meet the earth's atmosphere head-on, the combined speed may reach about 44 miles per second (71 kilometers per second).
Notes and References
http://www.nasa.gov/worldbook/meteor_worldbook.html
http://curious.astro.cornell.edu/question.php?number=478
