chapter 19 stars, galaxies, and the universe

Question 1

spectrum

Answer 1

the band of color produced when white light passes through a prism

Question 2

apparent magnitude

Answer 2

the brightness of a star as seen from the Earth

Question 3

absolute magnitude

Answer 3

the brightness that a star would have at a distance of 32.6 light-years fro Earth

Question 4

light-year

Answer 4

the distance that light travels in one year; about 9.5 trillion kilometers

Question 5

parallax

Answer 5

an apparent shift in the position of an object when viewed from different locations

Question 6

red giant

Answer 6

a large, reddish star late in its life cycle

Question 7

white dwarf

Answer 7

a small, hot, dim star that is the leftover center of an old star

Question 8

H-R diagram

Answer 8

Hertzsprung-Russell diagram, a graph that shows the relationship between a star’s surface temperature and absolute magnitude

Question 9

main sequence

Answer 9

the location on the H-R diagram where most stars lie

Question 10

supernova

Answer 10

a gigantic explosion in which a massive star collapses and throws its layers into space

Question 11

neutron star

Answer 11

a star that has collapsed under gravity to the point that the electrons and protons have smashed together to form neutrons

Question 12

pulsar

Answer 12

a rapidly spinning neutron star that emits rapid pulses of radio and optical energy

Question 13

black hole

Answer 13

an object so massive and dense that even light cannot escape its gravity

Question 14

galaxy

Answer 14

a collection of stars, dust, and gas bound together by gravity

Question 15

nebula

Answer 15

a large cloud of dust and gas in interstellar space; a region in space where stars are born or where stars explode at the end of their lives

Question 16

globular cluster

Answer 16

a tight group of stars that looks like a ball and contains up to 1 million stars

Question 17

open cluster

Answer 17

a group of stars that are close together relative to surrounding stars

Question 18

quasar

Answer 18

a very luminous, starlike object that generates energy at a high rate; quasars are thought to be the most distant objects in the universe

Question 19

cosmology

Answer 19

the study of the origin, properties, processes, and evolution of the universe

Question 20

big bang theory

Answer 20

the theory that states the universe began with a tremendous explosion 13.7 billion years ago

Question 21

How does color indicate the temperature of a star?

Answer 21

red and yellow stars burn cooler than blue stars

Question 22

How can a scientist identify a star’s composition?

Answer 22

Because different elements absorb different wavelengths of light, astronomers can tell what elements a star is made of from the light they observe from the star

Question 23

How do scientists classify stars?

Answer 23

Stars are classified by temperature, brightness, and size.

Question 24

How do astronomers measure distances from Earth to stars?

Answer 24

Astronomers use the unit light-year to tell distance between Earth and stars. They use the star’s parallax and math to calculate the actual distance to stars that are close to Earth. A star with a large parallax is closer to Earth than a star with a small parallax.

Question 25

What is the difference between apparent motion and actual motion of stars?

Answer 25

The apparent motion of objects in the sky is related to Earth's motion rotating on its axis. Each star is moving in space, but because they are so far away it is hard to see.

Question 26

How is brightness of stars measured?

Answer 26

The brightest stars in the sky are called first-magnitude. The dimmer the star, the larger the magnitude is. Using just our eyes, the dimmest stars we can see are sixth magnitude. Using large telescopes, scientists can see stars as dim as 29th magnitude.

Question 27

Name different types of stars.

Answer 27

main-sequence, giant, supergiant, white dwarf

Question 28

nuclear fusion

Answer 28

the process in which hydrogen changes to helium when a star becomes denser and hotter

Question 29

blue stars

Answer 29

very massive blue stars are not in the main sequence very long. They quickly use up the hydrogen in their cores, expand, and turn into giants or supergiants.

Question 30

White dwarf stars

Answer 30

small, hot stars | leftover centers of old stars

Question 31

the Sun

Answer 31

an average star main sequence is 1 solar diameter and has 1 solar mass

Question 32

giants and supergiants

Answer 32

an old star that has run out of hydrogen, the center shrinks inward and the outer parts expand outward

Question 33

red dwarf stars

Answer 33

low-mass stars | remain on main sequence a long time

Question 34

identify 3 types of galaxies

Answer 34

spiral, elliptical, irregular

Question 35

describe the contents and characteristics of galaxies

Answer 35

galaxies are composed of billions of stars and some planetary systems too.

Question 36

spiral galaxy

Answer 36

example: Andromeda | have a bulge at the center and spiral arms made up of gas, dust, and new stars

Question 37

elliptical galaxy

Answer 37

example: M87 massive blob 1/3 of all galaxies very bright centers with very little dust and gas

Question 38

irregular galaxy

Answer 38

example: Large Magellanic Cloud | galaxies that don't fit into any other class

Question 39

describe the big bang theory

Answer 39

13.7 billion years ago all the contents of the universe was compressed under extreme pressure, temperature, and density in a very tiny spot. Then the universe rapidly expanded and matter began to come together and form galaxies.

Question 40

What evidence supports the big bang theory?

Answer 40

in 1964 two scientists found radiation coming from all directions in space. One explanation for this radiation is that it is cosmic background radiation left over from the big bang.

Question 41

describe the structure of the universe.

Answer 41

the universe has a structure that is loosely repeated over and over again.

Question 42

what are 2 ways scientists calculate the age of the universe?

Answer 42

by measuring the distance from Earth to various galaxies by calculating the ages of old, nearby stars

Question 43

what will happen if the universe expands forever?

Answer 43

if the universe expands forever, stars will age and die and the universe will become cold and dark after many billions of years.