Asteroids - Introduction

• General Information
• Asteroids are rocky and metallic objects that orbit the Sun which are too small to be considered planets.
• They are known as minor planets
• Range in size from diameters of 1000 km down to pebble size.
• 16 asteroids are 240 km or bigger.
• Most exist in a main belt which lies between Mars and Jupiter.
• Most asteroids follow a slightly elliptical, stable orbit which takes them around the Sun every 3-6 years.
• The total mass of all the asteroids put together would form an object about half the diameter of our moon.
• Terms
• Asteroid: Rocky or metallic object which is too small to be a planet and is not a comet.
• Meteoroid: A piece of interstellar matter which is too small to be an asteroid and is on a collision course with Earth.
• Meteorite: A meteoroid that makes it through the Earth's atmosphere without burning up, and actually strikes the Earth's surface.
• Micrometeoroid: Particles or cosmic dust grains which are even smaller than meteoroids.
• Origins/Theories
• Asteroids are material left over from the formation of the solar system.
• Much of our understanding about asteroids comes from examining meteorites.
• One theory suggests that they are the remains of a planet which was destroyed in a massive collision.
• Another theory suggests that they are material which never coalesced into a planet, perhaps due to Jupiter's strong gravity.
• Scientists are very interested in asteroids because they consist of material from the very early solar system.

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