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Astro 1 Unit 1 Exam > Unit 3 Exam > Flashcards

Unit 3 Exam Flashcards

1
Q

What is the sun?
a. It is a star just like the stars we see in the nighttime sky
b. It is a special star, much more powerful than any other
c. It is the largest planet in our Solar System

A

a

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2
Q

Like how we humans, and animals, etc all glow in …
a. visible light
b. infrared
c. ultraviolet
d. x-rays
e. gamma rays

A

b

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3
Q

The Sun is 109 times the radius of Earth. Let’s see, that would mean you could fit about … Earth’s inside the Sun’s volume!
a. a hundred
b. a thousand
c. ten thousand
d. a million
e. a billion

A

d

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4
Q

What about the mass– 333,000 Earths? About how much of the total mass of all the objects in the solar system is contained in the Sun, alone?
a. 10%
b. 25%
c. 50%
d. 75%
e. 99%

A

e

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5
Q

We’ve been peeling the sun layers apart to see what makes it tick, but what physical process could generate that kind of energy?
a. burning coal
b. nuclear fission
c. nuclear fusion
d. matter-antimatter collisions
e. ten billion hamsters on exercise wheels

A

c

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6
Q

Can you tell me how many protons a hydrogen atom has, and how many protons a helium atom has?
a. Hydrogen has 2, and Helium has 1 proton
b. Hydrogen has 1, and Helium has 4 protons
c. Hydrogen has 2, and Helium has 4 protons
d. Hydrogen has 1, and Helium has 2 protons
e. Hydrogen has 1, and Helium has 1 proton

A

d

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7
Q

In the Sun the proton-proton-chain makes 4He the dominant form of Helium. 4He has…
a. two protons, because it is helium, and two neutrons to make 4 total particles in the nucleus
b. two protons, because it is helium, and one neutron to make 1 total particle in the nucleus
c. one proton, because it is helium, and three neutrons to make 4 total particles in the nucleus
d. three protons, because it is helium, one neutron to make 4 total particles in the nucleus
e. four protons and no neutrons

A

a

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8
Q

What is the first step in the p-p chain?
a. Helium-3 combines with Helium-3 to make Helium-6
b. a proton combines with a proton to make Hydrogen-2 (Deuterium)
c. Helium-4 splits apart into two protons and two neutrons
d. Hydrogen-2 combined with a proton to make Helium-3
e. Helium-3 combines with Helium-3 to make Helium-4 and 2 protons

A

b

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9
Q

What happened to the protons during the first step of the p-p chain?
a. the proton reacted with the other proton to make Helium-4
b. the proton converted to a neutron and then flew off into space
c. there was a big burst of energy and then Helium-3 was produced
d. energy was lost from the proton and it slowed down and decayed
e. one of the protons converted into a neutron, still contained with the Hydrogen-2

A

e

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10
Q

Why was there a big burst of energy in the first step of the p-p chain?
a. because the mass of the particles starting the reaction is more than that of its products. Mass converted to energy via E=mc^2
b. Because it is so hot in the core of the Sun so there was an explosion
c. because the mass of the sun is so large that the core was collapsing under intense gravity and then bounced back out
d. because the mass of the particles that came out of the reaction is more than that of the particles going into the reaction
e. because of the impact of the collision

A

a

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11
Q

What is the second step in the p-p chain reaction?
a. Helium-3 combines with Helium-3 to make Helium-6
b. a proton combines with a proton to make Hydrogen-2(Deuterium)
c. Helium-4 splits apart into two protons and two neutrons
d. Hydrogen-2 combined with an additional proton to make Helium-3
e. Helium-3 combines with Helium-4 to make Helium-7

A

d

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12
Q

What happened during the second step of the p-p chain?
a. again there is some energy release (a gamma-ray photon) and we end up with Helium-3
b. Helium-3 combines with Helium-3 to make Helium-6
c. a proton combines with a proton to make Hydrogen-2(Deuterium)
d. Helium-4 splits apart into two protons and two neutrons and energy is lost
e. Helium-3 combines with Helium-4 to make Helium-7

A

a

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13
Q

What is the final step in the p-p chain?
a. Helium-3 combines with another Helium-3 to make Helium-6
b. a proton combines with a proton to make Hydrogen-2(Deuterium)
c. Helium-4 splits apart into two protons and two neutrons
d. Hydrogen-2 combined with a proton, to make Helium-3
e. Helium-3 combines with another Helium-3 to make Helium-4 (and two protons are left over)

A

e

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14
Q

What else is seen in the final step of the p-p chain?
a. again a burst of energy is released and we end up with Helium-3
b. Helium-3 combines with Helium-3 to make Helium-6
c. a proton combines with a proton to make Hydrogen-2(Deuterium)
d. again a burst of energy is released and Helium-4 is produced, with two protons moving off to the side
e. Helium-3 combines with Helium-4 to make Helium-7

A

d

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15
Q

What is the general result of a proton-proton chain?
a. Fe -> H + He +Li +Be +…
b. 4H -> He + energy + other products
c. Au -> Ag + Pt
d. 2H -> Li + other products
e. 2 He -> 8H + energy + other products

A

b

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16
Q

The corona of the sun:
a. is its coolest layer
b. is its convective region
c. is visible during a solar eclipse
d. is the region in which nuclear reactions occur
e. is its densest layer

A

c

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17
Q

In the convective zone of the Sun:
a. the temperature is higher than in any other region
b. photons produced in the core pass freely through to the surface
c. Nuclear reactions convert Helium to Carbon
d. columns of hot gas rise, cool, and descend
e. nuclear reactions convert hydrogen to helium

A

d

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18
Q

What part of the Sun do we typically see?
a. Corona
b. Photosphere
c. Inner Core
d. Convection Zone
e. Radiation Zone

A

b

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19
Q

In nuclear fusion, energy is produced because…
a. gravity leads to collapse
b. the mass of the reacting chemicals is larger than that of the products
c. hydrogen is not stable
d. positrons are produced
e. of the energetic impact of collisions

A

b

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20
Q

So “luminosity” refers to …, whereas “brightness” must mean …
a. apparent output as observed at some distance/ absolute power output at the source
b. absolute power output at the source/ apparent output as observed at some distance

A

b

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21
Q

After doubling the distance from the light source, the bottom telescope’s brightness readout …, to about … the top detector’s value.
a. increased… twice
b. decreased… half
c. decreased… one quarter
d. increased … three times
e. decreased… one tenth

A

c

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22
Q

On tripling the distance from the light source, the bottom detector’s readout is …, to about … the top detector’s value.
a. decreased … one-third
b. decreased … half
c. increased … twice
d. decreased … one-ninth
e. increased … four times

A

d

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23
Q

A large luminosity star…
A: is always at a larger distance than a small luminosity star
B: emits more light than a low luminosity star
C: is always redder than a star with a small luminosity
D: is at a lower temperature than a small luminosity star
E: is always at a smaller distance than a small luminosity star

A

B

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24
Q

If a red giant appears the same brightness as a red main sequence star, which one is farther away?
A: the red giant
B: we can’t tell
C: it depends on the phase of the Moon
D: the main sequence star
E: they are at the same distance

A

A

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25
Q

The heaviest nuclei of all are formed …
A: during helium burning
B: as part of the p-p chain
C: during carbon burning
D: during a supernova explosion
E: during all stages of stellar evolution of massive stars

A

D

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26
Q

Fill in the blank in the following chemical reaction that occurs in the Sun: Hydrogen-2 + proton = _____ + energy:
A: Hydrogen-2
B: Hydrogen-1
C: Helium-3
D: Carbon-12
E: Helium-4

A

C

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27
Q

Which of the following has the smallest radius?
A: type A main sequence star
B: main sequence star with surface temperature 8000 K
C: type K main sequence star
D: white dwarf
E: a neutron star

A

E

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28
Q

Why does the main sequence part of a star’s life end?
A: The Helium in the core is exhausted.
B: The gravitational force is no longer large enough to balance the pressure.
C: The Hydrogen in the core is exhausted.
D: The temperature drops so that nuclear reactions are no longer possible.
E: Much of the mass of the star has evaporated.

A

C

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29
Q

Which of the following will have the shortest lifetime on the main sequence?
A: main sequence star with surface temperature 20000 K
B: main sequence star with surface temperature 3000 K
C: main sequence star with luminosity one-tenth that of the Sun
D: the Sun
E: main sequence star with mass 2 times the Sun

A

A

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30
Q

Many of the brightest 100 stars viewed from Earth are not on the main sequence (even though most stars are) because:
A: only high mass stars formed near to us in the Galaxy.
B: the most luminous stars are giants and supergiants that have already finished their main sequence lifetimes.
C: our region of the Galaxy is very young.
D: the main sequence is the shortest part of a star’s life so stars do not spend much time there.
E: our region of the Galaxy is very old.

A

B

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31
Q

A 2-solar mass main sequence star is at the same distance as a 0.2-solar mass main sequence star. Which star appears brighter?
A: depends on the phase of the Moon
B: the 2 solar mass main sequence star appears brighter
C: the stars are approximately the same brightness
D: the 0.2 solar mass main sequence star appears brighter
E: we cannot tell with the information given

A

B

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32
Q

The temperature of the photosphere of the Sun is closest to …
A: 107 Kelvin
B: 106 Kelvin
C: 100 Kelvin
D: 600,000 Kelvin
E: 6000 Kelvin

A

E

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33
Q

An estimate of the number of communicating/technological civilizations that we expect in our Galaxy would have a larger number if …
A: the average lifetime of a communicating civilization was smaller
B: the star formation rate in our Galaxy was smaller
C: the average number of planets that could support life for each star was larger
D: it was more difficult for life to develop intelligence, once life had formed
E: a smaller percentage of stars formed planets

A

C

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34
Q

If the Sun had twice its mass, then which of the planets would be in its habitable
zone?
A: Mercury
B: Venus
C: Earth
D: Neptune
E: Jupiter

A

E

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35
Q

In the transit method of finding extrasolar planets, the distance of the planet from its star is found from:
A: Kepler’s 3rd law using the period of the planet’s orbit (how often a transit
occurs).
B: The luminosity of its star divided by 4 pi times the radius squared.
C: the spectral type of the star, which is related to which chemical elements are present at different temperatures
D: what fraction of the light of the star is blocked by the planet when a transit
occurs
E: the Drake equation

A

A

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36
Q

How do astronomers measure the temperature of stars?
A: The inverse square law is used.
B: Temperature is determined from the radius of the star that is measured by radar.
C: By looking at which absorption lines are present in the star’s spectrum.
D: The rate of change of the color of the star is measured.
E: By comparing the luminosity and apparent brightnesses

A

C

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37
Q

If two stars are the same temperature, how can one be more luminous than the other?
A: It can have a larger reaction rate in the core.
B: It can be a different spectral type.
C: It can have stronger magnetic fields.
D: It can be closer
E: It can have a larger radius.

A

E

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38
Q

The largest fraction of nearby stars (e.g., within 100 light years) are …
A: neutron stars
B: Sun-like stars
C: blue main sequence stars
D: red main sequence stars
E: blue supergiants

A

D

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39
Q

Which of the stars in the diagram above is the hottest?
A: A
B: B
C: C
D: D
E: E

A

D

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40
Q

If they were all formed at the same time, which of the stars in the diagram above will live the longest?
A: A
B: B
C: C
D: D
E: E

A

B

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41
Q

The parallax angle of a nearby star is measured to be 0.02 arcseconds. What is the distance to the star?
A: 20 parsecs
B: 2 light years
C: 50 parsecs
D: 0.2 light years
E: 200 light years

A

C

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42
Q

Which of the following is the sequence of events for a 40-solar mass star (one of the most massive stars)?
A: planetary nebula, protostar, Sun-like star on main sequence, blue giant,
red giant
B: stellar nursery, protostar, Sun-like star on main sequence, red giant,
planetary nebula, white dwarf
C: stellar nursery, blue giant, Sun-like star on main sequence, red giant,
Type II supernova, neutron star
D: stellar nursery, protostar, blue star on main sequence, Type II supernova,
black hole
E: black hole, neutron star, white dwarf, Sun-like star on main sequence,
red giant, Type II supernova

A

D

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43
Q

Star A is 9 times more luminous than Star B. The two stars appear the same
brightness. What is true about their distances?
A: Star A is 9 times farther away than Star B.
B: Star B is 9 times farther away than Star A.
C: Star A is 3 times farther away than Star B.
D: Star B is 3 times farther away than Star A.
E: Stars A and B are at the same distance.

A

C

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44
Q

In the p-p chain, shown in the above diagram, what particles must be input in order to produce one 4He nucleus?
A: 8 protons, but 2 of them are returned when the 4He is produced
B: 6 protons, but 2 of them are returned when the 4He is produced
C: 2 photons and 2 positrons
D: 2 protons and 4 neutrons
E: 4 neutrons

A

B

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45
Q

What is the name of the slightly cooler layer of the Sun just outside the
photosphere?
A: core
B: corona
C: convective zone
D: chromosphere
E: radiative zone

A

D

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46
Q

How does a star move on the H-R diagram during the period of time it is converting
hydrogen to helium in its core?
A: It moves from the lower right of the diagram to the upper left of the diagram,
along the main sequence.
B: It moves from the upper left of the diagram to the lower right of the diagram,
along the main sequence.
C: It remains at a certain point on the main sequence and does not move on
the H-R diagram.
D: It moves from the upper right of the diagram to the lower left of the diagram.
E: It moves from the lower left of the diagram to the upper right of the diagram.

A

C

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47
Q

If the entire mass of Earth were concentrated in a region the size of a marble, the resulting object would be:
A: a Sun-like star
B: a white dwarf
C: a neutron star
D: a black hole
E: a planetary nebula

A

D

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48
Q

How does the sun maintain stability?

A

balance of gravity (inward force) and pressure of gas (outward force)

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49
Q

At what temperature does gas pressure provided by nuclear fusion in the Sun’s core happen at?

A

15 million degrees Kelvin

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50
Q

The diameter and mass of the Sun in comparison to the Earth

A

109 x Earths
333,333 x Earths

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51
Q

What is the luminosity of the Sun in 100 Watt Light Bulbs?

A

4 x 10^24

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52
Q

How much of the Solar system’s mass is made up by the Sun?

A

99.9%

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53
Q

The Sun has been shining for … years, and will continue to shine for … years

A

4.5 billion
5.5 billion

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54
Q

What are sunspots?
How long do they last?

A

Slightly cooler regions on the Sun’s surface
11 year cycles

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55
Q

What causes sun spots?

A

magnetic activity preventing hot material from rising in that region

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56
Q

What is a long-lasting source of energy in stars?

A

Nuclear Fusion

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57
Q

What is nuclear fusion?

A

4 protons combine to make helium-4
(2 protons and 2 neutrons) and release energy in gamma rays

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58
Q

Although the p-p chain initially requires … of energy to cause the high-speed collisions between proton and nuclei during each step in the reaction, … of energy is generated and released in every step

A

a lot
a little bit

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59
Q

Where does the energy output from the p-p chain come from

A

E=mc^2

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60
Q

The mass of Helium-4 is … then the mass of 4 protons; some of that mass is … into energy in the form of …-… …

A

less
converted
gamma-ray photons

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61
Q

layers of the sun from the inside to outside

A

core, radiative zone, convective zone, photosphere, chromosphere, flare, prominence, corona, solar wind

62
Q

what layer of the sun is at the center; high density and temperature; where nuclear reactions occur and gamma rays are produced

A

core

63
Q

what layer of the sun is where photons are repeatedly re-absorbed and re-emitted; the energy of an individual photon can take on average of 170,000 years to pass through

A

radiative zone

64
Q

what layer of the sun is where hot gas rises and cold gas sinks; light traverses in about 1 week

A

convective zone

65
Q

what layer of the sun is where the temperature 5,780 K; this is the “surface” of the Sun that we see;
photons have been converted to visible wavelengths; can see “granules” due to convection bringing material up and down in cells

A

photosphere

66
Q

what layer of the sun is where the red or orange color is; temperature about 4,500 K; we see through this, down to the photosphere

A

chromosphere

67
Q

what layer of the sun is characterized by an eruption coming out of Sun due to magnetic activity

A

flare

68
Q

what layer of the sun is comprised of hoop-shaped eruption out of the Sun due to magnetic activity

A

prominence

69
Q

what layer of the sun is low density; temperature about 1 million K; visible during solar eclipses

A

corona

70
Q

what layer of the sun is how charged particles coming from Sun’s surface, escaping to deep space; permeates the whole Solar System

A

solar wind

71
Q

What is the absolute power output, at the source (e.g., a star’s surface)

A

Luminosity

72
Q

What is the is apparent output, as observed at some distance ( “d “ ) away

A

Brightness

73
Q

What determines how bright a star appears, based upon its
luminosity (intrinsic brightness) and its distance?

A

Inverse-Square Law

74
Q

What is the inverse-Square Law?

A

Brightness=Luminosity/(4)(pi)(diameter)^2
or
Brightness= Luminosity/(diameter)^2

75
Q

If two stars have the same luminosity and one is ten times farther away than the other how will it appear?

A

1/10^2 as bright (100 times dimmer)

76
Q

If star A is 4 times as luminous as star B, then stars A and B would appear
equally bright if star A was … times as far away as star B

A

2

77
Q

What is this method called? The basic concept is to view a star from two locations on opposite sides of the Sun (Earth, but 6 months apart), and look for minute changes in its apparent position.

A

Parallax Method to Measure Distances

78
Q

The location for the parallax method to measure distance in Earth’s orbit are on opposite sides of what?

A

the “baseline”

79
Q

Some simple small-angle trigonometry can approximate …

A

distances to nearby stars

80
Q

What is the baseline for stellar parallax measurements (average distance between the Earth and Sun)?

A

1 AU

81
Q

What stars are not on the main-sequence?

A

red giants, super giants, and white dwarfs

82
Q

What type of stars are burning helium or even heavier elements in their cores
(not hydrogen anymore); starting to die; size is large, so they are very luminous even though they are relatively cool; top right of H-R diagram?

A

red giants and super giants

83
Q

What type of star is hot, small and dim, so they fall on lower left of H-R diagram; the cooling and fading cores left over from expired low-mass stars

A

white dwarfs

84
Q

what is the region around a star where liquid water could be present on a
planet’s surface — not too hot as to be all boiled off or dried out, and not too cold as to be permanently frozen over?

A

habitable zone

85
Q

a less-massive star would have habitable zone … to the star

A

closer

86
Q

a more-massive star would have habitable zone … from the star

A

farther

87
Q

It is commonly assumed that life requires … …, even life on Earth can
be found in some … environments: deep underground; in near or total darkness; high acidity; high radiation; in methane ice; extreme heat and/or pressure

A

liquid water
extreme

88
Q

a method to estimate the number, N, of communicating / technological civilizations in our galaxy at a given time

A

Drake Equation

89
Q

What does N stand for in the Drake equation(N = R * × fp × ne × fl × fi × fc × L)?

A

the current number of “intelligent,”
“communicating” civilizations in the
Milky Way Galaxy

90
Q

What does R stand for in the Drake equation(N = R * × fp × ne × fl × fi × fc × L)?

A

the rate of formation of “habitable”
stars in the galaxy (number per year)

91
Q

What does fp stand for in the Drake equation(N = R * × fp × ne × fl × fi × fc × L)?

A

= the fraction of these stars (in R*) that
form planetary systems

92
Q

What does ne stand for in the Drake equation(N = R * × fp × ne × fl × fi × fc × L)?

A

= the average number of Earth-like
planets in these systems (from fp)

93
Q

What does fl stand for in the Drake equation(N = R * × fp × ne × fl × fi × fc × L)?

A

the fraction of these planets (from ne)
on which life actually develops

94
Q

What does fi stand for in the Drake equation(N = R * × fp × ne × fl × fi × fc × L)?

A

the fraction of planets with life that
eventually give rise to “intelligent” life
fc = the fraction of intelligent species that

95
Q

What does fc stand for in the Drake equation(N = R * × fp × ne × fl × fi × fc × L)?

A

the fraction of intelligent species that
develop into technological civilizations
capable of interstellar communication

96
Q

What does L stand for in the Drake equation(N = R * × fp × ne × fl × fi × fc × L)?

A

the average lifetime of communicating,
technological civilizations (in years)

97
Q

True or False: Several extrasolar planets have been discovered in the habitable zones around their
stars

A

True, but it has been hard to determine whether they are “Earth-like” with regard to other properties.

98
Q

Who discovered and confirmed in 1992 the first extrasolar planets?

A

by Penn State Professor Alex Wolszczan

99
Q

What were the first extrasolar planets found orbiting?

A

a dead neutron star rather than a “normal” star

100
Q

Many of the extrasolar planets discovered in the late 1990s and early 2000s were planets around the mass of … that are very … to their parent stars.

A

Jupiter (or larger)
close

101
Q

thousands of extrasolar planets have been discovered since the early 2000s, mostly by the … …

A

“Kepler” mission

102
Q

The transit method uses Kepler’s 3rd law to find the distance of the planet from its star, again with …; then the planet’s temperature can be calculated (based on …, and the star’s …& …) to see if it is in that star’s habitable zone; the amount of drop in the star’s brightness can also tell the planet’s
size.

A

P^2= a^3
distance
star’s luminosity
spectral type

103
Q

What is the equation for the Parallax Method to Measure Distances?

A

Distance(parsecs) = 1 / parallax angle(arcsecs)

104
Q

a star with measured parallax angle of 0.1 arcsec is how many parsecs away?

A

10 parsecs (1 / 0.1 = 10)

105
Q

a star with a parallax angle of 0.02 arcsec is how many parsecs away?

A

50 parsecs (1 / 0.02 = 50)

106
Q

What does the H-R diagram stand for?
What is the horizontal axis?
What is the vertical

A

Hertsprung-Russell Diagram
Stars’ surface temperature(increasing from right to left)
Luminosity(expressed in terms of luminosity of the sun)

107
Q

cooler stars are …, hotter stars are …

A

redder(2300 K), bluer(40000 K)

108
Q

a star’s effective surface temperature is estimated using what?

A

spectral class

109
Q

The major spectral classes of stars from hottest to coolest?

A

O - B - A - F - G - K - M (“Only bored astronomers find gratification knowing mnemonics”)

110
Q

What determines a star’s spectral class?

A

It’s absorption spectrum (where absorption lines from different chemical elements with different levels of ionization arise
at different temperatures)

111
Q

What is the closest star from the sun, at 4.3 light years (1.35 parsecs)?

A

Alpha Centauri(in a triple star system with its brightest one similar to the sun)

112
Q

most of the nearest stars are … and …, they fall on what part of the H-R diagram?

A

cool and dim
Lower right side (most stars have these general properties)

113
Q

What is the brightest star in the nighttime sky?

A

Sirius(“Dog Star”), twice as massive as the Sun, binary companion is one white dwarf star

114
Q

The “brightest stars” (that is, as we see them from Earth) have … … properties.

A

more varied (red and blue, low and high luminosity, with some on the lower right of the H-R diagram, but others near where the Sun is some on the upper left, and some on the upper right (red giant region))

115
Q

The “brightest stars” tend to be biased towards stars that already have … …, so that they appear bright to us even at large distances; we simply … …
low-luminosity stars if they are too far away (even if greater in number)

A

high luminosities
cannot see

116
Q

What are the properties of a star?

A

luminosity, mass, size, temperature, and age

117
Q

Size and temperature directly affect what property of a star?

A

Luminosity(L is proportional to R^2 x T^4)

118
Q

a larger size = larger light-emitting surface area=?

A

greater luminosity

119
Q

higher temperature = ?(also peaks in bluer colors)

A

much greater luminosity

120
Q

Where are main-sequence stars located on the H-R diagram?

A

in a band from the lower right across to
upper left

121
Q

When on the main sequence (which occupies the majority of a star’s lifetime), what are stars doing?

A

stars are burning Hydrogen into Helium in their cores (by the p-p chain)

122
Q

For stars on the main sequence, higher … stars have a higher luminosity.

A

temperature

123
Q

Cool, faint, and small stars on the lower right of the H-R diagram

A

red dwarfs

124
Q

hot, bright and large stars on the upper left of the H-R diagram

A

blue giants

125
Q

What determines where on the main sequence a star lives and what the main sequence lifetime is for the star?

A

mass

126
Q

What type of main sequence stars are on the upper left of H-R diagram; masses ranging from about 0.1 to 100 times the mass of the Sun; sizes range from 0.1 to 15 times the radius of the Sun?

A

more-massive main sequence stars

127
Q

Luminosities of main sequence stars range from … to … times that of the Sun.

A

10^–3 to 10^6

128
Q

ages of main-sequence stars range from a … … … for more-massive stars to … … … … … …— the current age of the Universe — for less-massive stars

A

few million years
much more than 14 billion years

129
Q

The more massive stars use their greater fuel supply … …

A

more rapidly

130
Q

What is the Sun’s history/sequence of events in its lifetime?

A

stellar nursery, protostar, main sequence, red giant, planetary nebula,
white dwarf

131
Q

What is the ejected envelope (the layers outside the core) of a low-to
intermediate-mass star

A

planetary nebula

132
Q

What kind of stars have a mass less than 8 % of the Sun, and never heat up enough to have nuclear reactions in their core; also called “failed stars”?

A

Brown Dwarfs

133
Q

What is the end state of the former star’s core ; held up against gravity not by gas pressure anymore, but by pressure of electrons; about the size of the Earth

A

white dwarf

134
Q

More-massive stars have a … … life on the main-sequence as a star’s mass increases

A

much shorter

135
Q

Much-more massive stars burn their hydrogen on the … …; when core hydrogen is exhausted, then helium burns in the core (while swelling into a … …)

A

main sequence
a red giant

136
Q

When much more massive stars have exhausted their core’s helium supply, then … …, and then even heavier … … (all while swelling even larger, into a red supergiant)

A

carbon burning
nuclei burning

137
Q

What is it called when concentric shells of fusion zones involving different chemical elements, with the heaviest going on towards the core

A

“onion-skin” model

138
Q

Much more massive stars stop burning around …, because it is very stable, and reactions involving it do not produce energy — instead, they cost more energy than they release, so
no further gas pressure support for the star against its own gravitational collapse

A

iron

139
Q

a violent explosion with the star’s core left behind; the explosion itself creates a short-lived highly energetic environment which briefly makes possible the fusion of elements heavier than iron — like gold, silver, etc.

A

“Type II” supernova

140
Q

if the remaining core is about 1.4 – 3 solar masses, it becomes a … … — radius of 5 – 6 km, or roughly “city-sized”

A

neutron star

141
Q

if the core’s mass > 3 solar masses, it becomes a … … —
infinitesimally small radius, “compressed to a point” of infinite density

A

black hole

142
Q

the end state of the highest-mass stars ( > about 40 solar masses), left behind after supernova explosion

A

black hole

143
Q

the gravity of these collapsed (very dense) objects is so great that even … cannot escape

A

light

144
Q

true or false: black holes “suck things in”; even if you are far enough away from them

A

false

145
Q

what is the spherical boundary around a black hole from within which
nothing can escape — not even light (i.e., the “escape velocity” within this distance … the speed of light — “nature’s speed limit,” nothing can go faster)

A

the event horizon
exceeds

146
Q

What can be used to measure a black hole’s mass (think back to Kepler’s Laws, in Unit 2)

A

the speed of the orbit of a star in a binary system with the black hole

147
Q

the intense gravity around a black hole warps …, so that a clock appears to … … as it falls in; that is, light’s delivery of the image of the clock to an observer outside is delayed more and more as the clock nears the event horizon

A

space
slow down

148
Q

a point of infinite density at the center of a black hole is called what?

A

singularity

149
Q

strong … … operate near a black hole, and objects are stretched out because the force on the nearer part can be so much greater than the force on farther parts

A

tidal forces

150
Q

If a star begins with a mass less than about 8 solar masses:
* the core becomes a … …— collapse stops because of degeneracy
pressure of electrons; core radius same as Earth’s.
* the star is surrounded by released outer layers — a … …

A

white dwarf
planetary nebula

151
Q

If a star begins with about 8 – 40 solar masses:
* final core-collapse is preceded by a … …
* the core becomes a … … — collapse stops because of degeneracy
pressure of neutrons; radius 5 – 6 km (city-size).

A

Type II supernova
neutron star

152
Q

If a star begins with more than about 40 solar masses:
* final core-collapse is preceded by a … …
* the core becomes a … … — collapse does not stop; all the mass
becomes concentrated at a singularity.

A

Type II supernova
black hole

Astro 1 Unit 1 Exam (5 decks)

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