Transcript Slide 1
Other Objects in the Solar System Chapter 24 Section 4 Comets • Bodies of rock, dust, methane, ammonia, and ice that orbit the sun in long ellipses. • Examples: – Haley’s Comet • Passes by the earth every 76 years (last seen in 1986). – Comet Hale-Bopp • Discovered headed toward the sun in 1995 by two amateur astronomers. Comets • Parts of a comet: – Head • Core – Solid part of the comet. – Usually between 1 and 100 km in diameter. • Coma – Spherical cloud of gas and dust surrounding the nucleus. – Formed when heat vaporizes ices of water, methane, and ammonia as the comet approaches the sun. – Can extend up to 1 million km form the nucleus. – Sunlight reflecting off the coma gives a comet its bright appearance. – Tail • Consists of gas and dust that stream out from the head of the comet. • Formed when the solar wind (electrically charged particles from the sun) push gas and dust away from the head of the comet. – Always trails away from the sun. • Can be more than 80 million km long. Comets • Oort Cloud – Proposed by Dutch astronomer Jan Oort. – A large collection of comets that surround the solar system outside the orbit of Pluto. – These comets are either pulled into smaller orbits by the gravity of the sun or are pulled out of the solar system by the gravity of nearby stars. Meteoroids • Small bits of rock or metal which move throughout the solar system. • Most are less than 1 mm in diameter. • Can be dislodged from comets or broken off of colliding asteroids. Meteor • A meteroid that is pulled into the atmosphere of the earth and burns up. – These meteroids enter the atmosphere of the earth at speeds of 15 km/s to 70 km/s • Meteor shower – Occurs when the Earth passes through the trail of an old comet. – Many meteors occur because of the particles left over from the passing of the comet. Meteorite • A meteor that does not burn up all the way in the atmosphere and ends up hitting the surface of the earth. Asteroids • Fragments of rock made of material similar to the material that formed the planets. – More than 50,000 asteroids have been found in our solar system. Asteroids • Asteroid Belt – Area between the orbits of Mars and Jupiter where most asteroids are found. • The asteroid belt extends about 150 million km between the two planets. • Asteroids might exist here because the massive gravity of Jupiter did not allow a planet to form at this position. • Asteroids in the asteroid belt range in size from tiny to 940 km in diameter (an asteroid named Ceres). Asteroids • NEAR – Near Earth Asteroid Rendezvous – Went into orbit around the asteroid 433 Eros on Feb. 14th, 2000. – Indicates that the asteroid is similar in composition to the most common meteorites that strike the earth and has a surface with many craters. – On Feb 12th, 2001 it became the first spacecraft to land gently on as asteroid.