Transcript File
Meteoroids, Meteors, Meteorites, Asteroids & Comets What are asteroids? An asteroid is a large rock in outer space. Some can be very large, while others are as small as a grain of sand. Due to their smaller size, asteroids do not have enough gravity to pull themselves into the shape of a ball. While most asteroids can be found in the Asteroid Belt, others are in strange orbits straying far from home. It is currently believed that at least 5000 asteroids cross the Earth's orbit, some coming very close. Don't worry though, asteroids and comets only hit the Earth every 100 million years or so. Asteroid Belt The asteroid belt is a doughnut-shaped group of small, rocky objects. Most of these objects orbit the Sun in a belt between Mars and Jupiter, but some are in other orbits. Asteroids that orbit near the Earth are called NEA's (Near Earth Asteroids). ASTEROID MARS BELT JUPITER Vocabulary ASTEROID – a large rock in outer space. GRAVITY – the invisible force between objects that makes objects attract each other. ~Asteroids are chunks of rock and metal that orbit around the Sun. ~ Scientists think that they are loose material that never formed into planets. ~ The Main Asteroid Belt is located between Mars and Jupiter. ~ More than 40,000 asteroids have been discovered. Meteoroids are… 3. pieces that come mostly from asteroids, but also from comets, the moon, and the planet Mars. About Meteoroids Click on the picture above. Meteoroids are small bodies that travel through space and orbit the sun. The fastest meteoroids travel at roughly 26 miles per second (42 km per second) through space. Meteors are… Meteors are meteoroids that have entered Earth’s atmosphere. The friction between the fast-moving meteor and the gas in the Earth's atmosphere causes intense heat; the meteor glows with heat and then burns. This glowing phase usually happens 50 to 68 miles (80 to 110 kilometers) above the Earth. CLICK HERE TO SEE A SHORT MOVIE SHOWING A METEOR “FIREBALL” MOVING THROUGH SPACE. Meteor Showers If you have a dark, clear sky you will probably see a few meteors per hour on an average night. During one of the annual meteor showers you may see as many as 100 per hour. Our word meteor comes from the Greek word meteoron which means "a thing in the sky." Meteorites are… One of the Martian meteorites is believed to show evidence of early life on Mars. Meteorites are meteors that have fallen to the Earth. At least 100 meteorites hit the Earth every year. Most meteorites burn up in the Earth's atmosphere; all that is left is a bit of dust. What are comets? Comets are small, icy bodies that orbit the sun. They are made up of a solid nucleus (ice, gas, and dust), a gaseous coma surrounding the nucleus, and extremely long tails (both dust and gas tails). The tails can be up to 250 million km long. Vocabulary COMET - A frozen chunk of ice and dust in outer space. “A Dirty Snowball” ORBIT - The path followed by an object in space as it goes around another object. Since comets have no light of their own, how are we able to see them? And the answer is... Comets reflect light from the Sun which makes them visible to us here on Earth. The correct answer is… Ice, Gas,& Dust A Comets Orbit Comets orbit the Sun in highly elliptical orbits. Their velocity increases greatly when they are near the Sun and slows down at the far reaches of the orbit. Since the comet is light only when it is near the Sun (and is it vaporizing), comets are dark (virtually invisible) throughout most of their orbit. Vocabulary ELLIPTICAL - Shaped like an egg. VELOCITY – quickness of motion. PICTURE OF COMET SHOEMAKER-LEVY 9 When the comet was observed, its train of 21 icy fragments stretched across 710 thousand miles (1.1 million km) of space, or 3 times the distance between Earth and the Moon. The comet was approximately 410 million miles (660 million km) from Earth when the picture was taken, on a mid-July collision course with the gas giant planet Jupiter.