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Chapter 21 Vocab

TermDefinition
Asteroid Millions of small, rocky objects called _______ orbit the Sun in the asteroid belt between the orbits of Mars and Jupiter.
Comet A _______ is made of gas, dust, and ice and moves around the Sun in an oval-shaped orbit.
Astronomical Unit An _______ is the average distance from Earth to the Sun--about 150 million kilometers.
Period of Revolution The time it takes an object to travel once around the Sun is its _______.
Period of Rotation The time it takes an object to complete one rotation is its _______.
Terrestrial Planet _______ are the planets closest to the Sun, are made of rock and metal, and have solid outer layers.
Greenhouse Effect The _______ occurs when a planet's atmosphere traps solar energy and causes the surface temperature to increase.
Galilean Moons The four largest moons of Jupiter--Io, Europa, Ganymede, and Callisto--are known as the _______.
Meteoroid A _______ is a small, rocky particle that moves through space.
Meteor A _______ is a streak of light in Earth's atmosphere made by a glowing meteoroid.
Meteorite A _______ is a meteoroid that strikes a planet or a moon.
Impact Crater An _______ is a round depression formed on the surface of a planet, moon, or other space object by the impact of a meteorite.
Created by: haydyn b.
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