Ch 21 Review

How many stars are in our solar system?

• 1
• 1 million
• Over 1 billion

Which characteristic of the Sun primarily determines the orbits of planets in our solar system?

• large volume
• mostly made of hydrogen
• strong gravitational field
• high surface temperatures

The diagram below shows a planet's orbit around the Sun. What does the blue arrow represent?

• the gravitational pull of the Sun
• the planet's orbital path
• the planet's path if Sun did not exist
• the planet's speed

Earth and its solar system are part of the _____________ _____________ galaxy, which is one of many galaxies in the universe.

• Milky Way
• Nebulae
• Solar System

Which shape best describes a planet's orbit?

• a circle
• an ellipse
• a straight line

Which statement is true of the orbits of all the planets in our solar system?

• They are circular and have variations in speed.
• They are circular and move at a constant speed.
• They are elliptical and have variations in speed.
• They are elliptical and move at a constant speed.

An ellipse is like a

• figure eight.
• stretched-out circle.
• straight line.

orbit close to the Sun and have rocky surfaces

• inner planets
• outer planets

have gaseous surfaces and more than one moon

• inner planets
• outer planets

Mercury, Venus, Earth, and Mars

• inner planets
• outer planets