Based on what we know using current technology, there are probably about ____ planets in our Milky Way galaxy.

• 1000

• 1 billion

• 10 billion

• 100 billion

Prior to the 1990's we had no means of detecting planets orbiting other stars.

• False

• True

Most of the planets found to date lie within about ___ light years from our Sun.

• 100

• 200

• 300

• none of the above

Planets that orbit stars make up what we call a _____ system.

What does the root word "sol" mean?

Heliocentric means ____ -centered.

An ____ is a planet that orbits another star other than our Sun.

• dwarf planet

• exoplanet

• interstellar planet

• none of the above

"Exo" means on the _____.

What is the other name for an Exoplanet?

Spitzer and Keppler are both _______ .

• Earth-based telescopes

• orbital telescopes

• orbital satellites

• none of the above