Chapter 21 - The Solar System

Which shape describes a planet's orbit?

• a circle
• an ellipse
• a straight line

Why is Venus hotter than Mercury?

• Venus's surface is covered with lava
• Venus has a strong greenhouse effect
• Venus is closer to the sun than Mercury is

How are the outer planets similar?

• They have solid surfaces
• They are about the same size
• They have armosperes that are mostly hydrogen

Pluto was known as a planet but is now a(n)

• asteroid
• meteoroid
• dwarf planet

An astronomical unit is the average distance

• from Earth to Mars
• from Earth to the Sun
• from Earth to the Moon

Orbit close to the Sun and have rocky surfaces

• outer planets
• inner planets
• dwarf planets

Have gaseous surfaces and more than one moon

• inner planets
• outer planets
• dwarf planets

Chunks of rocks and ice that form a belt just beyond Mars

• asteroids
• comets
• meteors

Light streaks in the atmosphere due to objects from space

• asteroids
• comets
• meteors

Objects made of ice, rock, and dust that glow near the Sun

• asteroids
• comets
• meteors