Meteor
How long
Sonic booms
Of the several 10s of tons of cosmic material entering Earth’s atmosphere each day, only about one ton reaches the surface.
An object’s chance of survival depends on its initial mass, speed and angle of entry, and friability (tendency to break up). Micrometeoroids radiate heat so effectively that they are dramatically slowed without being vaporized and fallMeteorite seen to fall. Such meteorites are usually collected soon after falling and are not affected by terrestrial weathering (Weathering = 0). Beginning in 2014 (date needs confirmation), the NomComm adopted the use of the terms "probable fall" and "confirmed fall" to provide better insight into the meteorite's history. If Click on Term to Read More as a continuous, gentle, invisible rain. Meteoroids with masses between 10-6 g and 1 kg tend to burn up completely as meteors. Friable meteoroids break up and are destroyed at altitudes of 80 to 90 km. Those which are tougher survive longer and produce fireballs as their surface undergo
melting and ablationGradual removal of the successive surface layers of a material through various processes. • The gradual removal and loss of meteoritic material by heating and vaporization as the meteoroid experiences frictional melting during its passage through the atmosphere. The resulting plasma ablates the meteor and, in cases where a meteor Click on Term to Read More at temperatures of several thousand degrees. If meteoroids avoid destruction high up, they enter the lower, denser part of the atmosphere where they are rapidly decelerated.
Most meteors become visible at around 60 miles (96.5 kilometers) up. Some large meteors splatter, causing a brighter flash called a fireballA fireball is another term for a very bright meteor, generally brighter than magnitude -4, which is about the same magnitude of the planet Venus as seen in the morning or evening sky. A bolide is a special type of fireball which explodes in a bright terminal flash at its end, often with visible fragmentation. Click on Term to Read More, which can often be seen during the day and heard up to 30 miles (48 km) away. On average, meteors can speed through the atmosphere at about 30,000 mph (48,280 kph) and reach temperatures of about 3,000 degrees Fahrenheit (1,648 degrees Celsius).
The term meteor does not refer to the asteroid, meteoroidSmall rocky or metallic object in orbit around the Sun (or another star). or large micrometeoroid itself, but to the light phenomenon (flash and/or streak of light) created during its high speed entry into a planet’s atmosphere when the ionized particles that are vaporized from that object’s outer layer interact with the planet’s atmosphere. Though most of these interstellar objects are only a few mm across, when their paths intersect a planet’s orbitThe elliptical path of one body around another, typically the path of a small body around a much larger body. However, depending on the mass distribution of the objects, they may rotate around an empty spot in space • The Moon orbits around the Earth. • The Earth orbits around Click on Term to Read More, they do so at such extreme speed that the object compresses the atmosphere in front of them. On Earth, this compression raises the surface temperature of the object to >2,000 K causing the object’s outer layer to continuously vaporize in a process called ablation. The vaporized atoms collide with air molecules to create an ionized “trail”, that produces the bright steak of light that is only ~1 m across but it can be many km (typically 20-30 km) long depending on the speed of the meteoroid. It may also display different colors, the result of the de-excitation of different atmospheric molecules. Most meteors appear at altitudes of 100 – 120 km (lower thermosphere) and will enter dark flight at an altitude of approximately 50 km (lower limit of the mesosphere) when the increasingly dense atmosphere has slowed the object below the speed where ablation can occur.
If we assume that the Earth moves around the SunOur parent star. The structure of Sun's interior is the result of the hydrostatic equilibrium between gravity and the pressure of the gas. The interior consists of three shells: the core, radiative region, and convective region. Image source: http://eclipse99.nasa.gov/pages/SunActiv.html. The core is the hot, dense central region in which the at about 30 km/sec (108,000 km/h or 67,000 mph) and the escape velocityVelocity that an object needs to escape the primary gravitational influence of a more massive object: where, m = the object's mass, r = distance from object's center, and G = gravitational constant of the larger object. Click on Term to Read More from the solar systemDefinable part of the universe that can be open, closed, or isolated. An open system exchanges both matter and energy with its surroundings. A closed system can only exchange energy with its surroundings; it has walls through which heat can pass. An isolated system cannot exchange energy or matter with (velocity of an object arriving from infinity) at the orbit of the Earth is 42 km/s (151,000 km/h or 94,000 mph), then we can determine the theoretical slowest and fastest velocity for a meteor entering Earth’s atmosphere.
- The fastest velocity will occur when the Earth and the meteor are moving towards each other on a direct collision course. So, the fastest theoretical entry velocity is 42 km/s + 30 km/s, an astounding 72 km/s (259,0000 km/h or 161,000 mph)!
- The slowest velocity will occur when the meteor is moving in from behind the Earth. So, the slowest theoretical entry velocity is 42 km/s – 30 km/s, a still impressive 12 km/s (43,000 km/h or 27,000 mph)!
A very large meteor is known as a fireball and is usually caused by a larger body. A meteoroid or asteroid the size of a boulder or car will produce a very large and bright fireball even in the daylight. (NOTE: The International Astronomical Union defines a fireball as “a meteor brighter than any of the planets” (magnitude -4 or greater)).
Large meteor events may produce meteorites, but the combination of ablation and fracturing causes more than 80% of the original mass (prior to atmospheric entry) to be lost. During atmospheric passage, the object also moves far faster than the speed of sound (0.343 km/s at 20 oC) thus compressing the sound waves of its entry and creating sonic booms of such magnitude that they can sometimes be destructive as was experienced in the Feb. 2013 in Russia during the fall of the Chelyabinsk meteoriteWork in progress. A solid natural object reaching a planet’s surface from interplanetary space. Solid portion of a meteoroid that survives its fall to Earth, or some other body. Meteorites are classified as stony meteorites, iron meteorites, and stony-iron meteorites. These groups are further divided according to their mineralogy and Click on Term to Read More. It is not unusual for these sonic booms to rattle windows when they pass over populated areas. Witnesses during the 1912 Holbrook meteorite showerThe near simultaneous fall of numerous meteorites after the fragmentation of a single asteroid or large meteoroid in the atmosphere due to the immense frictional stresses encountered during atmospheric passage. A meteorite shower will produce a strewnfield that stretch for 10s if not even 100s of km. Some famous meteorite Click on Term to Read More are said to have heard a protracted rumble which lasted roughly 2 minutes.
Video of Chely HERE
