AST EXAM 3

Question 1

what two physical processes balance each other to create the condition known as gravitational equilibrium in stars?

Answer 1

gravitational force and outward gas pressure

Question 2

T/F: nuclear power plants on earth create energy in the same way as the sun

Answer 2

false

Question 3

from center outward, which of the following lists the layers of the sun in the correct order

Answer 3

core, radiation zone, convection zone, photosphere, chromosphere, corona

Question 4

why do sunspots appear dark?

Answer 4

they are regions that are significantly cooler than the rest of the photosphere

Question 5

the sun has enough nuclear fuel to last for another

Answer 5

5 billion years

Question 6

suppose you try to bring two protons close together, because of the electromagnetic force, the two protons will

Answer 6

repel on another

Question 7

what is the approx temp of the sun’s core

Answer 7

15 million K

Question 8

the star Alpha Centauri A is the same type of star as the sun, but its luminosity is about 1.6 times that of the sun, what can we conclude

Answer 8

ACA fuses hydrogen into helium in its core at a higher rate than our sun

Question 9

approximately, what is the sun made of

Answer 9

70% H, 28% HE, 2% other elements

Question 10

based on its surface temp of 6,000K, most photons that leave the sun’s surface lie in which region of the electromagnetic spectrum

Answer 10

visible

Question 11

true or false: the corona and chromosphere are hotter than the photosphere

Answer 11

true

Question 12

what is the solar wind

Answer 12

a stream of charged particles flowing outward from the surface of the sun

Question 13

which of the following is the phase of matter in the interior of the sun

Answer 13

plasma

Question 14

if the suns surface cooled, how would its appearance change

Answer 14

it would appear more red

Question 15

the suns surface is called the

Answer 15

photosphere

Question 16

true or false: the sun rotates more quickly at the equator than at the poles

Answer 16

true

Question 17

by what process does the sun generate energy

Answer 17

nuclear fusion

Question 18

what happens to energy in the sun’s convection zone

Answer 18

energy is transported outward by the rising of hot plasma

Question 19

if star A is closer to us that Star B, then star A’s parallax angle is

Answer 19

larger than that of Star B

Question 20

the spectral sequence sorts stars according to

Answer 20

surface temps

Question 21

the faintest star visible to the naked eye has an apparent magnitude of about

Answer 21

6

Question 22

star A has a absolute magnitude of 3, and star B has an absolute magnitude of 5, which star is brighter in our sky

Answer 22

there is not enough info to answer the question

Question 23

which of the following is the most numerous type of main-sequence star

Answer 23

an M star

Question 24

which of the following stars has a spectrum that peaks at the shortest wavelength

Answer 24

a blue star

Question 25

which of the following best describes the axes of a Hertzsprung-russel disgram

Answer 25

surface temperature on the horizontal axis and luminosity on the vertical axis

Question 26

ten parsecs is about

Answer 26

32.6 light-years

Question 27

on a H-R diagram, stellar radii

Answer 27

increase diagonally from the lower left to the upper right

Question 28

the total amount of power that a star radiated into space is called its

Answer 28

luminosity

Question 29

the stellar spectral sequence, in order of decreasing temperatures is

Answer 29

OBAFGKM

Question 30

which star is the hottest star

Answer 30

O

Question 31

which of the following luminosity classes refers to stars on the main sequence

Answer 31

V

Question 32

on a H-R diagram, where would you find stars that are cool and luminous

Answer 32

upper right

Question 33

on a main sequence ,stars obtain their energy

Answer 33

by converting hydrogen to helium

Question 34

you observe a star and you want to plot it on a H-R diagram, you will need to measure all of the following, except the star's

Answer 34

mass

Question 35

how is the lifetime of a star related to its mass

Answer 35

more massive stars live much shorter lives than less massive stars

Question 36

which of the following statements about spectral types of stars is not generally true

Answer 36

the spectral type of a star can be used to determine its distance

Question 37

The basic fusion reaction through which the Sun produces energy is __________.

Answer 37

Four hydrogen nuclei fuse to make one helium nucleus

Question 38

The energy that is released in the hydrogen fusion reaction comes from __________.

Answer 38

The difference in mass between the four hydrogen nuclei and the single resulting helium nucleus

Question 39

Place the layers of the Sun into the correct order from innermost at left to outermost at right.

Answer 39

Core, Radiation zone, convection zone, photosphere, chromosphere, corona

Question 40

All the phenomena of solar activity — including sunspots, flares, coronal mass ejections, and the sunspot cycle — are tied to changes in the Sun's __________.

Answer 40

magnetic field

Question 41

Rank the layers of the Sun based on their density, from highest to lowest.

Answer 41

Core, radiation zone, convection zone, photosphere, chromosphere, corona

Question 42

In which of the following layer(s) of the Sun does nuclear fusion occur?

Answer 42

core

Question 43

What two items on the list below are in balance in what we call gravitational equilibrium?

Answer 43

gas pressure and gravity

Question 44

To place a star on an H-R diagram, we must know its __________.

Answer 44

surface temp and luminosity

Question 45

On the H-R diagram, most stars fall into the region labeled ____________.

Answer 45

main sequence

Question 46

Compared to a high-luminosity main-sequence star, stars in the upper right of the H-R diagram are __________.

Answer 46

cooler and larger in radius

Question 47

Compared to a low-luminosity main-sequence star, stars in the lower left of the H-R diagram are __________.

Answer 47

hotter and smaller in radius

Question 48

what is the fate of an isolated brown dwarf

Answer 48

it will remain a brown dwarf forever

Question 49

which of the following masses separates low mass stars from high mass stars

Answer 49

about 2 solar masses

Question 50

how does the surface temp and luminosity of a protostar compare to the surface temp and luminosity of the main sequence star it becomes

Answer 50

a main sequence star is hotter and dimmer than it was as a protostar

Question 51

what core temp is required before hydrogen fusion can begin in a star

Answer 51

Ten mil K

Question 52

what is a protostar

Answer 52

a star that is still in the process of forming

Question 53

what would happen if the sun was a black hole

Answer 53

NOTHING

Question 54

what is the max mass of a white dwarf

Answer 54

1.4

Question 55

max mass of a neutron star?

Answer 55

3

Question 56

Stars that are fusing hydrogen in their cores are

Answer 56

main-sequence stars

Question 57

what is a nova

Answer 57

The temperature of accreted matter eventually becomes hot enough for hydrogen fusion. Fusion begins suddenly and explosively

Question 58

what is a massive star super nova

Answer 58

Iron core of a massive star reaches white dwarf limit and collapses into a neutron star, causing total explosion.

Question 59

what is a white dwarf supernova

Answer 59

Carbon fusion suddenly begins as a white dwarf in close binary system reaches white dwarf limit, causing total explosion.

Question 60

what is the mass of the sun

Answer 60

2 X 10 to the 30 kg

Question 61

what is the rotation period of the sun

Answer 61

25 days

Question 62

true or false: bigger stars are built faster than smaller stars

Answer 62

TRUE

Question 63

what are sunspots

Answer 63

Are cooler than other parts of the Sun’s surface (4000 K) Are regions with strong magnetic fields

Question 64

a neutron star is

Answer 64

the core remnant of a star that died in a massive star supernova

Question 65

which of the following is closest in mass to a typical white dwarf

Answer 65

the sun

Question 66

the minimum mass of a black hole that forms during a massive star supernova is roughly

Answer 66

3 solar masses

Question 67

a white dwarf is mostly made of

Answer 67

carbon

Question 68

what triggers a nova explosion

Answer 68

hydrogen gas from a companion star builds up on the surface of the white dwarf and when the temp gets high enough, it fuses to helium

Question 69

true or false: our sun will likely undergo a nova event in about 5 billion years

Answer 69

false

Question 70

true or false:the remnant left behind by a white-dwarf supernova is a neutron star

Answer 70

false

Question 71

true or false: there is no upper limit to the mass of a neutron star

Answer 71

false

Question 72

which of the following best describes a black hole

Answer 72

a place from which the escape velocity exceeds the speed of light