Chapter 31.3

Question 1

large groups of stars, dust, and gas; held together by gravity

Answer 1

Galaxy

Question 2

spiral galaxy that is about 100,000 light-years in diameter and contains from 200-400 billion stars, including the sun

Answer 2

Milky Way

Question 3

group of fifty galaxies including the Milky Way

Answer 3

Local group

Question 4

study of how the universe began, what is made of, and how it continues to evolve

Answer 4

Cosmology

Question 5

theory about 13.7 billion years ago, the entire universe was contained in a single point that began expanding outward

Answer 5

Big Bang Theory

Question 6

residual radiation from the formation of the universe; predicted by the big bang theory and later detected in 1965

Answer 6

Cosmic Background Radiation

Question 7

Type of matter that cannot be seen and can only be detected by its gravitational effects

Answer 7

Dark Matter

Question 8

Energy that might be causing the accelerating expansion of the universe

Answer 8

Dark Energy

Question 9

How long ago did the Big Bang occur?

Answer 9

13.7 billion years