रविवार, 17 फ़रवरी 2013

Asteroid ,meteorites ,bolide

Asteroid ,meteorites ,bolide 

Small pieces of  space debris -usually parts of comets or asteroids -that are on a collision course with the earth are called meteorides.They become meteors when they enter the Earth's atmosphere .Extremely bright meteors -whether they strike the earth's surface (meteorites )or not -that can be seen like a fire ball streaking through the sky are known as bolides .Most meteors burn up in the atmosphere ,but if they survive the frictional heating and strike the surface of the Earth they are called meteorites .

So the Friday morning (Fe15,2013)event was not an asteroide or a meteorite ,but a meteor or ,to be precise a bolide.

A large meteor that explodes in the atmosphere is called a bolide.It is a synonym for a fire ball .

 There is no consensus on its definition, but we use it to mean an extraterrestrial body in the 1-10-km size range, which impacts the earth at velocities of literally faster than a speeding bullet (20-70 km/sec = Mach 75), explodes upon impact, and creates a large crater. "Bolide" is a generic term, used 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.

What is mach number ?

This refers to the speed of an aircraft moving equal to or faster than the local speed of sound in air at that temperature .

Mach number  is the ratio of aircraft speed to that of sound there at that temperature .An aircraft moving as fast as mach 1 is moving with the speed of sound .An aircraft moving with mach number greater than 5 is hypersonic.

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