Chapter 17 study guide
_____________ are the larger, outer planets that are made mostly of hydrogen and helium gases.
Gas planets
The _________________________________states that the strength of gravity depends on the mass of the objects and the distance between them.
law of universal gravitation
A(n) _________________ is a massive object orbiting a star like the sun.
planet
______________ are made mostly of rock and metal and are known as the terrestrial planets.
Inner planets
Most _____________s are less that a kilometer in diameter.
asteroids
The _________________of a planet is an imaginary line through its center from pole to pole.
axis
A(n) _____________'s tail faces away from the sun and can stretch for millions of kilometers into space.
comet
The shape of a planet's orbit is not a perfect circle but an ________________.
ellipse
The force of attraction between all objects is known as ________________.
gravitational force
A chunk of burning rock traveling through Earth's atmosphere is called a(n)___________________.
meteor
Unlike a meteor, a(n) _______________ passes through Earth's atmosphere and strikes the surface.
meteorite
Planets follow a regular, repeating path around the sun called a(n) ______________
orbit/revolution
An object that is in orbit around another object is called a(n) ______________________.
satellite
The ________________________ includes the sun and objects that are gravitationally bound to it.
solar system
The distance from Earth to the Sun or 1.0______ is equal to 150 million kilometers.
A.U/one astronomical unit