2016 Jan

Physics of Falling Stars

January 13, 2016

Physics of Meteors

Meteor shower is a spectacular phenomenon observed in the night sky. Watching the trails of falling stars that last for a split-second is a delightful experience. A meteor, also called as falling star or shooting star is space dust or space rocks that enter atmosphere of earth during earth’s movement through this debris as a part of revolutionary motion around sun. Generally meteors do not reach earth as they disintegrate in the atmosphere on their way to earth’s surface. But those rocks that reach earth are called as meteorites. But what causes the disintegration of these rocks? And why do some of them manage to survive? The answers are discussed in the current article.

Atmosphere of earth consists of various gases like nitrogen, oxygen, and carbon dioxide in large amounts along with oxides of nitrogen, ozone, water vapor, etc, in small quantities. The particles present in gases, gas molecules, move randomly in all directions. When these moving particles hit an object, force is exerted on the object. The more particles an object is hit with, the more force is applied. The force applied also depends on the mass of these particles and the velocity at which they hit the object. This force applied per unit area is called as pressure applied. A bunch of gas molecules when placed inside a container exert pressure on the container and that’s the reason why a balloon filled with gas is inflated. As what we have learnt about the gas laws during our H2 Physics tuition classes, when pressure is increased with volume of the container remaining constant, the temperature of the container increases. This increase in temperature is because of increased number of collisions of gas molecules with the container surface.

A similar mechanism comes to work when a space rock or space dust enters the atmosphere of earth. The debris does not experience such pressurized environment in space as it is largely vacuum. As soon as it enters earth’s atmosphere, the object encounters gas molecules hitting it. This process is called as aerodynamic heating. Since the space rocks move at very high speed (as large as 70,000 kilometers per hour) the velocity with which it hits gas molecules or vice-versa is very high. Because of this constant bombarding by the gas molecules, the rock gets heated up and glows, just like heated iron. As the temperatures go up to extreme levels, the rock disintegrates and causes the formation of trail. Some rocks are too large that a part of it reaches earth intact even if most it is disintegrated in the process. The similar phenomenon is observed when space shuttles enter earth’s atmosphere. Space shuttle Columbia’s disaster, in which all the crew members were killed, was caused due to damaged heat insulators.

Watch out for the Perseids Meteor Shower in 2016!

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