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