Module 11 Flashcards
1
Q
What are the four key quantum effects in astronomy discussed?
A
Degeneracy pressure, quantum tunneling, virtual particles, evaporation of black holes.
2
Q
What principle explains the resistance to compression in electrons within a plasma?
A
Exclusion principle.
3
Q
What type of pressure is dominant at low to moderate densities?
A
Thermal pressure.
4
Q
Fill in the blank: The pressure that arises from the crowding of electrons is called _______.
A
degeneracy pressure.
5
Q
How does degeneracy pressure relate to an electron’s position and momentum?
A
Highly compressed electrons must move quickly due to the uncertainty principle.
6
Q
What happens to a star when it reaches the limit of electron degeneracy pressure?
A
It collapses into a neutron star.
7
Q
What is neutron degeneracy pressure?
A
Pressure caused by neutrons at high densities, preventing further collapse.
8
Q
True or False: Neutron degeneracy pressure can grow infinitely strong.
A
False.
9
Q
What catastrophic event occurs when a high-mass star’s core collapses?
A
Supernova explosion.
10
Q
What is released during the collapse of a stellar core when electrons combine with protons?
A
Neutrinos.
11
Q
What is the Crab Nebula?
A
A supernova remnant from the explosion observed in A.D. 1054.
12
Q
Fill in the blank: The event when a star explodes is called a _______.
A
supernova.
13
Q
What is the significance of Supernova 1987A?
A
It was the first supernova observed in four centuries, providing unique study opportunities.
14
Q
What historical records document the Crab Nebula supernova?
A
Chinese, Japanese, and Arabic writings.
15
Q
Fill in the blank: The gravitational collapse of a core releases an enormous amount of _______.
A
energy.
16
Q
What phenomenon allows elements created in a star’s nuclear furnace to be scattered into space?
A
Supernova explosion.
17
Q
What is the relationship between neutron stars and degeneracy pressure?
A
Neutron stars are supported by neutron degeneracy pressure.
18
Q
How do the elements from a supernova contribute to new star formation?
A
They mix with other gases in interstellar space to form new stars.
19
Q
What astronomical event is expected when Betelgeuse explodes?
A
It will be as bright as the full moon.
20
Q
What is the role of neutrinos in a supernova explosion?
A
They provide energy to the shock wave that propels the star’s outer layers outward.
21
Q
What was a significant finding from Supernova 1987A?
A
A burst of neutrinos was recorded, confirming that the explosion released most of its energy in the form of neutrinos
Neutrino detectors in Japan and Ohio captured this data.
22
Q
What is the primary source of energy during the collapse of a stellar core?
A
Neutrinos are released during the collapse, suggesting the core undergoes sudden collapse to a ball of neutrons
23
Q
What is the role of neutron telescopes in astronomy?
A
They are designed to study events in the distant universe and were spurred by the neutrino data from Supernova 1987A
24
Q
How does a star’s mass determine its life cycle?
A
A star’s birth mass governs how nuclear fusion progresses in the core
25
What happens to low-mass stars at the end of their life cycle?
They die in planetary nebulae, leaving behind white dwarfs composed mostly of carbon
26
What type of star is left behind after a high-mass star undergoes a supernova?
A neutron star or a black hole
27
What is the Algol paradox?
It describes how a less massive star in a binary system can become a subgiant while a more massive star remains a main-sequence star
28
What are tidal forces in the context of binary star systems?
They occur when the gravity of each star attracts the near side of the other star more strongly than the far side
29
What is mass exchange in binary star systems?
It occurs when gas from the outer layers of a giant star spills onto its companion star
30
What is a white dwarf?
The exposed core of a star that has died and shed its outer layers in a planetary nebula
31
What type of pressure supports a white dwarf against gravity?
Electron degeneracy pressure
32
What is the typical composition of a white dwarf left behind by a star like the Sun?
Mostly carbon
33
How does the density of a white dwarf compare to that of the Sun?
A typical white dwarf has the mass of the Sun compressed into a volume the size of Earth
34
What is the white dwarf limit?
The maximum mass of a white dwarf, approximately 1.4 times the mass of the Sun
35
What happens to a white dwarf in a close binary system?
It can gain mass from its companion star
36
What is an accretion disk?
A whirlpool-like disk formed when mass spills over from a companion star to a white dwarf
37
True or False: More massive white dwarfs are larger in size than less massive white dwarfs.
False
38
What is the relationship between the mass of a white dwarf and its size?
More massive white dwarfs are actually smaller in size and denser
39
What causes the luminosity of red giants to increase as they age?
The increase in mass of the inert helium core causes the surrounding hydrogen-fusing shell to become hotter and increase its fusion rate
40
What is the primary mechanism that allows gas particles in a white dwarf's accretion disk to spiral inward?
Friction caused by differences in orbital speeds
## Footnote
Gas in the inner region of the disk orbits faster than gas in the outer region, leading to energy loss.
41
How do the sizes and temperatures of protostellar disks compare to those of accretion disks around white dwarfs?
Accretion disks around white dwarfs are smaller and hotter than protostellar disks
## Footnote
The stronger gravity of white dwarfs results in higher orbital speeds and temperatures.
42
What type of radiation can be emitted by the accretion disk around a white dwarf due to friction?
Visible and ultraviolet light, and sometimes x-rays
## Footnote
The heat generated by friction in the disk can lead to these emissions.
43
What phenomenon is described as sudden increases in brightness of a binary system, potentially by a factor of 10 or more?
Dwarf novae
## Footnote
These events occur when matter falls suddenly onto the white dwarf's surface.
44
At what temperature does hydrogen fusion ignite on the surface of a white dwarf?
About 10 million K
## Footnote
This ignition occurs when enough hydrogen has accumulated in a thin surface layer.
45
What is the difference between a nova and a supernova?
A nova is a minor detonation of hydrogen fusion on a white dwarf, while a supernova is the total explosion of a star
## Footnote
Novae are less luminous than supernovae.
46
What happens to the white dwarf during a nova event?
It ejects most of the material that has accreted onto it
## Footnote
This results in a nova remnant that may remain visible for years.
47
What primarily determines the time between successive novae in a binary system?
The rate at which hydrogen accretes onto the white dwarf's surface
## Footnote
Also influenced by how compressed the hydrogen becomes.
48
What is the white dwarf limit?
The maximum mass a white dwarf can reach before it explodes in a supernova
## Footnote
This limit is approximately 1.4 solar masses.
49
What occurs when a white dwarf reaches the white dwarf limit?
Carbon fusion ignites, leading to a white dwarf supernova
## Footnote
This is similar to the helium flash in low-mass red giants but releases much more energy.
50
How can two white dwarfs in a binary system lead to a white dwarf supernova?
They may merge if gravitational waves cause them to spiral inward
## Footnote
If their total mass exceeds 1.4 solar masses, the merger results in a supernova.
51
What distinguishes white dwarf supernovae from massive star supernovae?
White dwarf supernovae lack hydrogen lines in their spectra
## Footnote
This is because white dwarfs contain very little hydrogen.
52
What is a neutron star?
A ball of neutrons created by the collapse of the iron core in a massive star supernova
## Footnote
Typically about 10 kilometers in radius but more massive than the Sun.
53
What provides the degeneracy pressure that supports neutron stars against gravity?
Neutron degeneracy pressure
## Footnote
This arises when neutrons are packed closely together.
54
What is the escape velocity at the surface of a neutron star?
About half the speed of light
## Footnote
This extreme gravity would immediately crush anything attempting to land on its surface.
55
What is the composition of matter near the surface of a neutron star?
Largely composed of electrons and positively charged atomic nuclei
## Footnote
Deeper inside, the matter is almost entirely neutrons.
56
Who discovered the first pulsar, and when?
Jocelyn Bell in 1967
## Footnote
She identified the regular radio wave pulses from a neutron star.
57
What phenomenon causes pulsars to emit regular pulses of radiation?
The rapid rotation of the neutron star and its strong magnetic field
## Footnote
This creates beams of radiation that sweep past Earth.
58
What happens to a pulsar's rotation rate over time?
It gradually slows down
## Footnote
This is due to the loss of energy and angular momentum from electromagnetic radiation.
59
What is a pulsar?
A pulsar is a rotating neutron star that emits beams of radiation, appearing to pulse as these beams sweep past Earth.
60
True or False: All neutron stars are pulsars.
False
61
What happens to a pulsar's rotation rate over time?
It gradually slows down due to the loss of energy and angular momentum from its magnetic field.
62
How fast does the pulsar in the Crab Nebula currently spin?
About 30 times per second.
63
What is the maximum spin rate for a white dwarf?
About once per second.
64
What is the significance of pulsar timing?
It allows for testing theories such as Einstein’s general theory of relativity and the discovery of extrasolar planets.
65
What are x-ray binaries?
Close binary systems consisting of a neutron star and a still-living star, emitting high-energy x-rays.
66
Fill in the blank: Accreting neutron stars release energy primarily in the form of _______.
x-rays
67
What is an x-ray burst?
A sudden spike in luminosity from an accreting neutron star, primarily releasing energy in x-rays.
68
What triggers an x-ray burst in a neutron star?
The ignition of helium fusion on the neutron star.
69
What is the event horizon of a black hole?
The boundary beyond which nothing can escape the black hole's gravity.
70
What is the Schwarzschild radius?
The radius of the event horizon of a black hole, depending only on its mass.
71
What happens to an object that crosses the event horizon?
It cannot escape and is lost to the observable universe.
72
What are the three basic properties of a black hole?
* Mass
* Electric charge
* Angular momentum
73
True or False: A black hole can retain information about the matter that falls into it.
False
74
What is a singularity in the context of a black hole?
A point where matter is crushed to an infinitely small and dense state.
75
What effect does a black hole's rotation have on spacetime?
It drags neighboring regions of spacetime around in circles.
76
How does the escape velocity from an object relate to its mass and size?
Escape velocity increases as an object becomes more compact.
77
What is an example of a binary system that has been used to test Einstein's theory?
Binary systems of neutron stars.
78
Fill in the blank: The first confirmed discovery of extrasolar planets was made using _______.
pulsar timing
79
What lies inside a black hole?
A singularity
## Footnote
A singularity is a point where matter is crushed to an infinitely tiny and dense point.
80
What is a singularity in the context of a black hole?
A point in a black hole where matter is infinitely dense
## Footnote
In rapidly rotating black holes, the singularity may take the shape of a ring.
81
Which two theories make different predictions about singularities?
Einstein's general relativity and quantum physics
## Footnote
General relativity predicts infinitely curved spacetime, while quantum physics predicts chaotic fluctuations.
82
What is the event horizon of a black hole?
A mathematical boundary beyond which nothing can escape
## Footnote
It is not a physical barrier.
83
What happens to time as one approaches a black hole?
Time runs more slowly due to gravitational effects
## Footnote
This is a prediction of Einstein's general relativity.
84
What is gravitational redshift?
The phenomenon where light shifts to red as it escapes a strong gravitational field
## Footnote
It occurs due to gravity rather than the Doppler effect.
85
What occurs to a clock falling into a black hole from an observer's perspective?
The clock appears to tick more slowly and eventually freezes
## Footnote
This is due to the increasing redshift of its light.
86
What lethal effect do tidal forces near a black hole have on an astronaut?
The astronaut is stretched lengthwise and squeezed from side to side
## Footnote
This is caused by the difference in gravitational pull on different parts of the body.
87
What is the Schwarzschild radius?
The radius defining the event horizon of a black hole
## Footnote
It is proportional to the mass of the black hole.
88
What causes a black hole to form from a massive star?
The collapse of a stellar core when neutron degeneracy pressure fails
## Footnote
This typically occurs during a supernova event.
89
What is the mass limit for neutron stars?
Between about 2 and 3 solar masses
## Footnote
Above this limit, neutron degeneracy pressure cannot prevent collapse.
90
How can black holes be detected if they emit no light?
By observing their gravitational influence on surrounding objects
## Footnote
This includes x-ray binaries and the dynamics of nearby stars.
91
What is Cygnus X-1?
An x-ray binary system that is a strong candidate for containing a black hole
## Footnote
The mass of its unseen companion exceeds the neutron star limit.
92
What type of events can produce gamma-ray bursts?
Explosions of extreme power, such as supernovae and mergers of neutron stars or black holes
## Footnote
Gamma-ray bursts are among the most energetic events in the universe.
93
True or False: A spaceship can easily fall into a black hole.
False
## Footnote
Spaceships can orbit safely unless they get too close to the black hole.
94
Fill in the blank: The gravitational force near a black hole is _____ than that of a neutron star.
stronger
95
What happens to a massive star during a supernova?
The core collapses into a neutron star or potentially a black hole
## Footnote
The explosion occurs when electron degeneracy pressure fails.
96
What is the relationship between energy and mass in Einstein's theory?
Energy is equivalent to mass
## Footnote
This means energy can exert gravitational attraction.
97
What is a supermassive black hole?
A black hole with a mass millions or billions of times that of the Sun
## Footnote
These are thought to reside at the centers of many galaxies.
98
What type of observational evidence supports the existence of black holes?
Gravitational waves and x-ray emissions from accretion disks
## Footnote
These observations indicate the presence of massive unseen objects.
99
What is a gamma-ray burst?
An explosion of almost unimaginable power representing the most powerful bursts of energy observed in the universe.
## Footnote
Gamma-ray bursts can fluctuate dramatically in intensity over short time periods.
100
What is the luminosity of a gamma-ray burst compared to the Milky Way?
It briefly exceeds the combined luminosity of a million galaxies like our Milky Way.
## Footnote
This luminosity is difficult to explain, suggesting gamma-ray bursts channel energy into narrow beams.
101
What causes some gamma-ray bursts?
Extremely powerful supernova explosions, particularly those forming black holes, known as hypernovae.
## Footnote
These events release significantly more gravitational potential energy than those forming neutron stars.
102
What is the primary evidence linking gamma-ray bursts to exploding stars?
Observations of gamma-ray bursts in other wavelengths, including visible light and x-rays.
## Footnote
Some gamma-ray bursts coincide with supernova explosions and are found in regions of active star formation.
103
What happens when neutron stars merge?
They emit gravitational waves, spiral together, and merge, releasing energy greater than that of a massive star supernova.
## Footnote
Neutron-star mergers can produce rare elements, including gold and platinum.
104
What significant event was detected on August 17, 2017?
The first detection of gravitational waves from a merger between two neutron stars.
## Footnote
This detection was confirmed by a burst of gamma rays seen by the Fermi satellite shortly after.
105
What happens when black holes merge?
They emit strong gravitational waves and can merge to form a more massive black hole.
## Footnote
The gravitational waves from black hole mergers can be detected from billions of light-years away.
106
What is a white dwarf?
The core left over from a low-mass star, supported by electron degeneracy pressure, typically with solar mass compressed to Earth size.
## Footnote
White dwarfs can undergo nova events when they acquire hydrogen from companions.
107
What is a neutron star?
A ball of neutrons created by the collapse of a massive star's iron core during a supernova.
## Footnote
Neutron stars resemble giant atomic nuclei and are extremely dense.
108
How are neutron stars discovered?
They are seen as pulsars, which emit beams of radiation due to their rapid spin and strong magnetic fields.
## Footnote
Pulsars provided the first direct evidence for neutron stars.
109
What can happen to a neutron star in a close binary system?
It can accrete hydrogen-rich material, forming x-ray binaries and resulting in x-ray bursts.
## Footnote
Helium fusion can ignite on the neutron star's surface in some systems.
110
What defines a black hole?
A region where gravity has crushed matter into oblivion, creating a hole from which nothing can escape, marked by the event horizon.
## Footnote
Black holes have three basic properties: mass, electric charge, and angular momentum.
111
What is the significance of the event horizon in a black hole?
It marks the boundary between the observable universe and the interior of the black hole.
## Footnote
The size of a black hole is characterized by its Schwarzschild radius.
112
What happens to objects falling into a black hole?
Time appears to run more slowly for the object, and light from it becomes increasingly redshifted.
## Footnote
The object never appears to pass through the event horizon; it disappears from view.
113
What causes gamma-ray bursts?
They are believed to come from powerful supernova explosions or mergers of neutron stars.
## Footnote
These bursts are the most powerful explosions observed in the universe.
114
What elements are primarily produced by neutron star mergers?
Gold, platinum, uranium, and various rare elements.
## Footnote
Models suggest that neutron-star mergers are the primary sources of these elements in the universe.
115
What was the first detection of gravitational waves?
Detected by LIGO in 2015 from the merger of two black holes.
## Footnote
The detection provided strong evidence for the existence of black holes.
116
What is the role of LIGO in astrophysics?
It detects gravitational waves from astronomical events, providing evidence for phenomena like black hole mergers.
## Footnote
LIGO's sensitivity has allowed it to measure vibrations of less than one part in a billion.
