31.3

Question 1

A large group of stars, dust, and gas held together by gravity.

Answer 1

Galaxy

Question 2

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

Answer 2

Milky Way

Question 3

A group of about 50 galaxies including the Milky Way.

Answer 3

Local Group

Question 4

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

Answer 4

Cosmology

Question 5

A theory that 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

A 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

What is the universe made up of?

Answer 9

Regular matter and Dark matter