Chapter 1: A Modern View of the Universe

Question 1

a star and all objects that orbit it

Answer 1

star system

Question 2

a great island of stars in space

Answer 2

galaxy

Question 3

the group of about 40 galaxies to which the Milky Way belongs

Answer 3

Local Group

Question 4

a collection of a few dozen or more galaxies bound together by gravity

Answer 4

galaxy clusters

Question 5

the largest known structures in the universe, consisting of many clusters of galaxies and individual galaxies

Answer 5

supercluster

Question 6

the sum total of all matter and energy

Answer 6

universe

Question 7

Earth’s average distance from the Sun; about 150 million kilometers

Answer 7

astronomical unit

Question 8

the distance that light can travel in one year; about 10 trillion kilometers

Answer 8

light-year

Question 9

the portion of the universe that can be seen from Earth

Answer 9

observable universe

Question 10

a large, glowing ball of gas that generates heat and light through nuclear fusion in its core

Answer 10

star

Question 11

a moderately large object that orbits a star and shines primarily by reflecting light from its star; must orbit its star, be large enough for its own gravity to make it round, and have cleared most other objects from its orbital path

Answer 11

planet

Question 12

an object that orbits its star and is massive enough for its gravity to have made it round, but has not cleared most objects from its orbital path

Answer 12

dwarf planet

Question 13

an object that orbits a planet

Answer 13

moon

Question 14

a relatively small and rocky object that orbits a star

Answer 14

asteroid

Question 15

a relatively small and ice-rich object that orbits a star

Answer 15

comet

Question 16

an asteroid, comet, or other object that orbits a star but is too small to qualify as a planet or dwarf planet

Answer 16

small solar system body

Question 17

the Sun and all the material that orbits it

Answer 17

solar system

Question 18

the spinning of an object around its axis

Answer 18

rotation

Question 19

the motion of one object around another due to gravity

Answer 19

orbit

Question 20

the increase in the average distance between galaxies as time progresses

Answer 20

expansion (of the universe)

Question 21

the event thought to mark the beginning of the universe

Answer 21

Big Bang

Question 22

the process in which lightweight atomic nuclei smash together and fuse to make heavier nuclei

Answer 22

nuclear fusion

Question 23

the plane of Earth’s orbit around the Sun

Answer 23

ecliptic plane

Question 24

the amount by which a planet’s axis is tilted with respect to a line perpendicular to the ecliptic plane

Answer 24

axis tilt