Comets, Asteroids, and Meteors
In the previous lesson we discussed the planets, which are the largest objects in our solar system. In this lesson we will look at some of the smallest objects in our solar system: Comets, Asteroids, and Meteors.
COMETS ARE A MIXTURE OF FROZEN GASES LIKE CO2, METHANE, AND AMMONIA MIXED UP WITH ICE AND ROCKY MATERIAL.
THEY ORBIT THE SUN ON HIGHLY ECCENTRIC ORBITS, USUALLY WITH VERY LONG PERIODS.
Comets are believed to come from 2 distinct areas of space.
- The Kuiper Belt is a ring of icy material beyond the orbit of Neptune. Comets that come from here have a period of about 200 years or less.
- At the very edge of our solar system is another source of comets called the Oort Cloud. Comets from the Oort Cloud have extremely long periods of well over 200 years.
Comets Change as they Approach the Sun
For most of a comet's life, all you would see of it is the icy nucleus. But when comets get close to the Sun they change dramatically.
The solar wind vaporizes the frozen gases in the nucleus creating a glowing cloud called a HALO around the nucleus.
The halo is pushed by the solar wind outward creating a TAIL THAT ALWAYS POINTS AWAY FROM THE SUN.
ASTEROIDS ARE ROCKY AND METALLIC BODIES RANGING IN SIZE FROM DUST GRAINS TO OVER 600 MILES ACROSS.
THOUSANDS OF THEM ORBIT THE SUN IN A BELT THAT LIES BETWEEN THE ORBITS OF MARS AND JUPITER.
Some asteroids, classified as NEAR EARTH OBJECTS, have orbits that bring them much closer to the Sun, sometimes very close to the Earth. Several times in our planet's history we have been struck by Asteroids entering the inner solar system.
- The Chicxulub crater in the Yucatan Penninsula in Mexico is evidence of of an asteroid impact that we believe caused widespread rapid climate change that may have led to the extinction of the dinosaurs. This occurred
- In 1908 another asteroid exploded just miles above the Tunguska region of Siberia.
- In 2013 another asteroid called Chelyabinsk exploded in the atmosphere above a Russian town injuring 1,500 people!
Meteoroids, Meteors, Meteorites
These three objects sound the same because they are indeed the same exact thing! We just call it different names based on where it is when we observe it.
- METEOROIDS ARE SMALL PIECES OF ROCK AND METAL FLOATING IN SPACE.
- METEORS ARE METEOROIDS THAT ENTER THE ATMOSPHERE AND BURN UP. When they enter the atmosphere, friction with air particles causes them to burn creating a bright streak in the night sky. They are often referred to as "SHOOTING STARS"
- METEORITES ARE THE DEBRIS LEFT OVER IF A METEOR MAKES IT ALL THE WAY THROUGH THE ATMOSPHERE AND IMPACTS THE EARTH.