Chapter 17

Scientists are researching a force called ___________ that could be pushing galaxies apart.

• dark energy
• kinetic energy
• potential energy

The Milky Way is part of a(n) cluster of about 30 galaxies called the ______________.

• Local Group
• Visiting Group
• Lost Group

The Milky Way is a(n) ____________ galaxy that contains gas, dust, and almost 200 billion stars.

• elliptical
• spiral
• irregular

Our planet, Earth, is part of a(n) solar system that is in the _______________galaxy.

• Andromeda Galaxy
• Milky Way
• Magellanic Clouds

Clusters clump into larger groups called _________________.

• massive clusters
• giant clusters
• superclusters

A(n) ________ galaxy can have the shape of a basketball or a football but lack internal structure.

• elliptical
• spiral
• irregular

A(n) _______ galaxy does not have a clear shape or structure.

• elliptical
• spiral
• irregular

A(n) _______ galaxy has a bulging central disk of stars with spiral arms that radiate from the central disk.

• elliptical
• spiral
• irregular

More than ______ percent of the universe’s mass is thought to be dark matter, but scientists do not know what type of material it contains.

• 10
• 90
• 100

The force that holds stars and galaxies together is _________________.

• glue
• magnetism
• gravity