Physical Science CH 20 The Universe

Astronomers estimate that the universe contains

• 100 galaxies

• 100 million galaxies

• 100 billion galaxies

• 100 trillion galaxies

Clusters of galaxies can form larger groups called

• supernovas.

• superclusters.

• constellations.

• supergiants.

The big bang theory states that the universe began with a gigantic explosion

• 4.4 billion years ago

• 13-15 billion years ago

• 50 billion years ago

• 100 billion years ago

All stars

• reflect light from the sun.

• appear to wander off their star paths.

• produce their own light.

• all of these.

All stars radiate

• heat energy

• electromagnetic waves

• light energy

• all of these

Stars are held together by

• ionic forces

• magnetic forces

• electrical forces

• gravitational forces

Nearly 90 % of all stars are at what point in their life cycles?

• infancy

• youth

• mid-life

• old age

Supergiant stars

• form from red giants

• fuse hydrogen into carbon

• form planetary nebulae

• form supernovas

Quasars are thought to be the centers of

• distant nebulas

• distant constellation

• distant galaxies

• distant clusters

The varying theories of the universe's eventual fate all depend on the universe's current

• rate of expansion.

• mass.

• volume.

• energy.