# Meteoroid

meteoroid is a small rocky or metallic body travelling through space. Meteoroids are significantly smaller than asteroids, and range in size from small grains to 1 meter-wide objects.Most are fragments from comets or asteroids, while others are collision impactdebris ejected from bodies such as the Moon or Mars.

From a meteoroid to a meteor and meteorite: how a meteoroid enters the atmosphere to become visible as a meteor and impact the Earth’s surface as a meteorite.

The visible streak of light from space debris is the result of heat as it enters a planet’s atmosphere, and the trail of glowing particles that it sheds in its wake is called a meteor, or colloquially a “shooting star” or “falling star”. A series of many meteors appearing seconds or minutes apart, and appearing to originate from the same fixed point in the sky, is called a meteor shower. Incoming objects larger than several meters (asteroids or comets) can explode in the air. If a meteoroid, comet or asteroid or a piece thereof withstands ablation from its atmospheric entry and impacts with the ground, then it is called a meteorite.

Around 15,000 tonnes of meteoroids, micrometeoroids and different forms of space dust enter Earth’s atmosphere each year.

Background

Meteor Shower Basics

### I am not an expert on meteors, so I needed to do some research. It turns out there are three sources of meteors:

• Asteroid belt

The asteroid belt is the source of the slow-moving meteors, which are assumed to originate from collision between objects in the asteroid belt. The Geminides are a good example of this type of meteor shower.

• Comets

Comets have often been compared to “dirty snowballs” that orbit the Sun. They release rocky material as the heat of the Sun causes them to slowly disintegrate. Comets are the source of the fast-moving meteors. The Leonids are a good example of this type of meteor shower.

• Outside of the Solar System

These are very rare and unpredictable, so they would not be part of any well-known meteor shower. However, their velocity could be very high as they would not be in orbit of the Sun (by definition) and would be following hyperbolic trajectories. I will not be addressing this case here.

Computing Escape Velocity

### where

• G is the universal gravitational constant.
• r is the meteor’s distance from the attracting body’s center of gravity.
• MBody is the mass of the attracting body.
• mMeteor is the mass of the meteor.
• FMeteor is force of attraction on the meteor.

### ${{E}_{Meteor}}=\int\limits_{\infty }^{{{R}_{Body}}}{-{{F}_{Meteor}}\left( r \right)}\cdot dr=G\cdot \frac{{{M}_{Body}}\cdot {{m}_{Meteor}}}{{{R}_{Body}}}$

where

• EMeteor is the work performed on the meteor by the attracting body.
• RBody is the radius of the attracting body (I am assuming the attracting body is spherical).

### wherevMeteoris the speed of the meteor. We will use Equation 3 to estimate the speed of the meteors entering our atmosphere.

Analysis

Asteroid-Based Meteor Shower

In this case, we assume that the meteor has somehow broken free of an asteroid with negligible velocity and has simply fallen to the Earth. This means that its velocity at the surface of the Earth will be the escape velocity from the Earth. Figure 2 illustrates the calculation.

Figure 2: Illustration of Velocity for a Meteor Originating in the Asteroid Belt.

This calculation explains the 11 km/s speed sometimes quoted for slow meteors.

Comet-Based Meteor Shower