8th Grade – Chapter 2 The Solar System
Vocabulary
Solar System – sun, planets, and all the other objects that revolve around the sun.
Nebular theory – theory which states that the solar system began as a huge cloud of dust
and gas called a nebula, which later condensed to form the sun and its
nine planets.
Orbit- path an object takes when moving around another object in space.
Period of revolution – time it takes a planet to make one revolution around the sun.
Period of rotation - time it takes a planet to make on rotation on its axis.
Retrograde rotation – reverse motion in which a planet rotates from east to west, instead
of from west to east.
Greenhouse effect – process by which heat is trapped by a planet’s atmosphere and
cannot return to space.
Asteroid belt - region of space between Mars and Jupiter in which asteroids are found.
Magnetosphere – magnetic field around a planet.
Comet – object made of ice, gas, and dust that travels through space.
Meteoroid – chunk of metal or stone that orbits the sun.
Meteor – streak of light produced by a meteoroid as it burns up in the Earth’s
atmosphere.
Meteorite – meteor that strikes the Earth’s surface.
Reaction engine – engine, such as a rocket, in which the rearward blast of exploding
gases causes the rocket to shoot forward.
Escape velocity – velocity needed to escape the Earth’s gravitational pull.