Units 6-23 Vocab Flashcards
(280 cards)
1
Q
1.4 solar masses; the theoretical maximum mass a white dwarf star can have and still remain a white dwarf
A
white dwarf limit
2
Q
The central region of a star, in which nuclear fusion can occur.
A
Core
3
Q
What method do we use to measure distances within the solar system?
A
Radar Ranging
4
Q
A particularly luminous type of pulsating variable star that follows Leavitt’s law (also called the period–luminosity relation) and hence is very useful for measuring cosmic distances
A
Cepheid variable stars
5
Q
3 different ways of measuring the amount of dark energy in clusters of galaxies?
A
from galaxy orbits, from the temperature of the hot gas in clusters, and from the gravitational lensing predicted by Einstein.
6
Q
A cluster of up to several thousand stars; l are found only in the disks of galaxies and often contain young stars.
A
Open clusters
7
Q
A graph plotting individual stars as points, with stellar luminosity on the vertical axis and spectral type (or surface temperature) on the horizontal axis.
A
An H-R diagram
8
Q
A method of measuring distances within the solar system by bouncing radio waves off planets.
A
Radar Ranging
9
Q
a particle not affected by the strong nuclear forces, but is only subjected to the weak forces; includes electrons and neutrons
A
Leptons
10
Q
a place where gravity has crushed matter into oblivion, creating a hole in the universe from which nothing can escape, not even light.
A
black hole
11
Q
a place where spacetime is curved so much that it essentially forms a bottomless pit, making it like a hole in spacetime.
A
Black Hole
12
Q
a process in which subatomic particles can “tunnel” from one place to another even when they don’t actually have enough energy to overcome an energy barrier between the two places.
A
Quantum tunneling
13
Q
A redshift caused by the fact that time runs slowly in gravitational fields.
A
Gravitational Redshifts
14
Q
A region in which energy is transported outward by convection.
A
Convection Zone
15
Q
a region of cosmic gas and dust formed from the cast-off outer layers of a dying star
A
planetary nebula
16
Q
A small, spectral type M star that displays particularly strong flares on its surface.
A
Flares star
17
Q
A spherically shaped cluster of up to a million or more stars; are found primarily in the halos of galaxies and contain only very old stars.
A
Globular clusters
18
Q
a standard relative to which motion and rest may be measured; any set of points or objects that are at rest relative to one another enables us, in principle, to describe the relative motions of bodies.
A
Frame of reference
19
Q
a star showing a sudden large increase in brightness and then slowly returning to its original state over a few months.
A
Nova
20
Q
A star system that contains two stars.
A
Binary star system
21
Q
A state of balance in which the force of gravity pulling inward is precisely counteracted by pressure pushing outward; also referred to as hydrostatic equilibrium.
A
gravitational equilibrium
22
Q
A sudden and dramatic expansion of the universe thought to have occurred at the end of the GUT era
A
inflation
23
Q
A supernova that occurs when an accreting white dwarf reaches the white dwarf limit, ignites runaway carbon fusion, and explodes like a bomb; often called a Type Ia supernova.
A
White Dwarf Supernova
24
Q
A Type Ia supernova; a type of supernova that occurs in binary systems in which one of the stars is a white dwarf.
A
white dwarf supernova
25
A type of fundamental particle that has extremely low mass and responds only to the weak force; they are leptons and come in three types— electron neutrinos, muon neutrinos, and tau neutrinos.
Neutrinos
26
a type of pressure that can occur even in the absence of heat. It arises from the combination of the exclusion principle and the uncertainty principle. It is the dominant form of pressure in the astronomical objects known as brown dwarfs, white dwarfs, and neutron stars.
Degeneracy pressure
27
a type of subatomic particle; includes a photon or meson whose spin quantum number is zero or an integral number.
Bosons
28
a type of subatomic particle; includes protons, neutrons, and electrons; whose spin quantum number is an odd multiple of 1/2.
Fermions
29
a very large star of high luminosity and low surface temperature. These stars are thought to be in a late stage of evolution when no hydrogen remains in the core to fuel nuclear fusion.
Red Giant
30
A way of classifying a star by the lines that appear in its spectrum; it is related to surface temperature. The basic spectral types are designated by letters (OBAFGKM, with O for the hottest stars and M for the coolest) and are subdivided with numbers from 0 through 9.
Spectral Types
31
A white dwarf in a close binary system can acquire hydrogen from its companion through an ______________ _______.
accretion disk
32
a ________-mass star begins hydrogen shell fusion and then goes through a series of stages, fusing successively heavier elements as its core temperature rises.
high
33
After energy emerges from the radiation zone, ___________ carries it the rest of the way to the photosphere, where it is radiated into space as sunlight.
Convection
34
an episode in which something is hotter for a limited time, something that can occur at various stages of stellar evolution.
Thermal pulses
35
An object for which we have some means of knowing its true luminosity, so that we can use its apparent brightness to determine its distance with the luminosity–distance formula.
Standard Candles
36
an underlying background energy that exists in space throughout the entire Universe.
vacuum energy
37
What type of star are the exposed cores of stars that have already died, meaning they have no further means of generating energy through fusion?
White dwarfs
38
Blotches on the surface of the Sun that appear darker than surrounding regions.
Sunspots
39
Bursts of charged particles from the Sun’s corona that travel outward into space.
Coronal Mass Ejections
40
By grouping galaxies according to luminosity and color, What color star-forming cloud do spiral and irregular galaxies belong to?
star-forming blue cloud
41
By grouping galaxies according to luminosity and color, What color star forming cloud do elliptical galaxies belong to?
non-star-forming red sequence
42
Caused by helium fusion igniting frequently on the neutron star’s surface; ccur in low-mass X-ray binary systems where a neutron star and low-mass main sequence star are in orbit around one another.
x-ray bursts
43
Does mass increase at speeds close to the speed of light?
YES
44
electromagnetism and the weak force became distinct at the end of the era.
Electroweak era
45
Equation that tells us that mass itself contains an enormous amount of potential energy.
E=mc^2
46
Era began at 10^–38 seconds to 10-10 second after the Big Bang, when the temperature of the universe cooled enough to separate the Strong Force from the Electroweak Force (the name for the two unified forces of Electro-magnetism and the Weak Nuclear Force). This Era contains two sub-eras - Inflation and Reheating.
Electroweak Era
47
Era prior to 10^-43 seconds after the Big Bang, when we believe that the four basic forces of nature, 1) gravity, 2) nuclear strong force, 3) nuclear weak force, and 4) electromagnetic force were combined into a single "super" force.The temperature of the universe was 1 x 10^32 degrees Celsius.
Planck era
48
At very high energy and temperature, the three fundamental forces (the Strong Nuclear Force, the Weak Nuclear Force, and Electro-magnetism) of the Standard Model are merged into one single force.Era begins at 10^-43 when gravity separates from the other three unified forces, which do remain unified. It ends when Inflation begins at 10^-38 seconds.
GUT era
49
explains three of the four fundamental forces that govern the universe: electromagnetism, the strong force, and the weak force.
standard model
50
Fusion of protons and neutrons into helium ceased at the end of the era
era of nucleosynthesis
51
Galaxies are neither disklike nor rounded in appearance
Irregular Galaxies
52
Galaxies are rounder and redder than spiral galaxies and contain less cool gas and dust.
Elliptical galaxies
53
Galaxies began to form at the end of the era.
era of nuclei
54
Galaxies with prominent disks and spiral arms
Spiral Galaxies
55
Gravity became distinct at the start of the era
GUT era
56
helium will begin to fuse into carbon by a reaction known as the triple-alpha process, because it converts three helium nuclei into one carbon atom.
helium fusion
57
How can we measure the masses of stars in a binary star system?
Using Newton’s version of Kepler’s third law if we can measure the orbital period and separation of the two stars.
58
How did ancient thinkers imagine the Sun as?
to be some type of fire, perhaps a lump of burning coal or wood.
59
How do elliptical galaxies tend to be grouped?
large clusters
60
How do spiral galaxies tend to be grouped?
they reside in relatively small groups
61
How does gravity affect time?
Time runs more slowly in places where gravity is stronger
62
How many different types of leptons are there?
6
63
How many different types of quarks are there?
6
64
How were Neutron stars discovered?
Through Pulsars
65
Hubble's Law equation
v= H0 x d
66
hydrogen fusion reactions taking place in a shell of hydrogen surrounding a core of helium or heavier elements in an ageing star
Hydrogen shell fusion
67
If you observe an object moving by you at high speed, how is its length and mass different than when at rest?
its length is shorter than its length when at rest, and its mass is greater than its mass when at rest.
68
If you observe an object moving by you at high speed, is its time running faster or more slowly than yours?
More slowly
69
In its final stages of life, a high-mass star’s core becomes what?
It becomes hot enough to fuse carbon and other heavy elements.
70
The type of geometry in which the rules of geometry for a flat plane hold, such as that the shortest distance between two points is a straight line and that the sum of the angles in a triangle is 180°.
Flat geometry
71
Instrument that has detected pulses of gravitational waves produced when orbiting neutron stars or black holes ultimately merge.
LIGO
72
Interior layers of the sun from inside, out?
core, radiation zone, convection zone, photosphere, chromosphere, and corona.
73
is a massive explosion of a dying star.
supernova
74
is a star—a giant ball of hot gas that generates light and shines it brightly in all directions.
Sun
75
made up of a normal star and a collapsed star (a white dwarf, neutron star, or black hole).
x-ray binary
76
marks the boundary between our observable universe and the inside of the black hole
Event Horizon
77
Mathematical expression of the idea that more distant galaxies move away from us faster: v = H0 × d, where v is a galaxy’s speed away from us, d is its distance, and H0 is Hubble’s constant.
Hubble's Law
78
Matter particles annihilated all the antimatter particles by the end of the era.
Particle era
79
molecules formed by atoms consisting of antiprotons, antineutrons, and positrons. Stable _________ does not appear to exist in our universe.
Antimatter
80
name given to the form of energy thought to be causing the expansion of the universe to accelerate.
Dark energy
81
name given to the unseen mass whose gravity governs the observed motions of stars and gas clouds.
Dark matter
82
occur in distant galaxies but shine so brightly in the sky that they must be the most powerful explosions we ever observe in the universe.
Gamma-ray bursts
83
Once the lowest energy level is filled, the other electrons are forced into higher and higher energy states resulting in them travelling at progressively faster speeds. These fast moving electrons create a pressure which is capable of supporting a star! What is this pressure called?
electron degeneracy pressure
84
Predicts the ratio of protons to neutrons during the era of nucleosynthesis, and from this predicts that the chemical composition of the universe should be about 75% hydrogen and 25% helium (by mass)
Big Bang Theory
85
Epoch prior to 10-43 s after the Big Bang, when we believe that the four basic forces of nature, 1) gravity, 2) nuclear strong force, 3) nuclear weak force, and 4) electromagnetic force were combined into a single "super" force.
Planck Epoch
86
Radiation left over from the Big Bang; Its spectrum matches the characteristics expected of the radiation released at the end of the era of nuclei, confirming a key prediction of the Big Bang theory.
cosmic microwave background
87
A region of the interior in which energy is transported primarily by radiative diffusion.
Radiation Zone
88
rapidly spiraling matter that is in the process of falling into an astronomical object; which matter swirls toward the white dwarf’s surface.
accretion disk
89
rotating neutron stars observed to have pulses of radiation at very regular intervals that typically range from milliseconds to seconds.
pulsars
90
Short-lived phenomena on the Sun, including the emergence and disappearance of individual sunspots, prominences, and flares; sometimes called solar weather.
Solar activity
91
Stars on the ________ _________ are all fusing hydrogen into helium in their cores.
main sequence
92
Stars that appear just below the supergiants on the H-R diagram because they are somewhat smaller in radius and lower in luminosity.
Giants
93
Stars that grow alternately brighter and dimmer as their outer layers expand and contract in size.
Pulsating Variable Stars
94
Stars with masses above 8Msun?
high mass stars
95
Stars with masses less than 2Msun?
low-mass stars
96
Epoch started about 10-35 seconds came to an end about 10-6 second. We begin to see the rapid formation of quarks and anti-quarks. The combination of quarks and gluons make-up protons and neutrons, but during this epoch they had too much energy to be confined inside them.
Quark Epoch
97
Tells us that if the universe were infinite, unchanging, and everywhere the same, the entire night sky would be as bright as the surface of the Sun, and it would not be dark at night.
Olbers’ paradox
98
tells us that two fermions of the same type cannot occupy the same quantum state at the same time. This principle does not apply to bosons.
exclusion principle
99
tells us that we cannot simultaneously know the precise values of an object’s position and momentum—or, equivalently, its energy and the precise time during which it has this energy.
uncertainty principle
100
The amount of light reaching us per unit area from a luminous object; often measured in units of watts/m2.
Apparent Brightness
101
The balance between the rate at which fusion releases energy in the star’s core and the rate at which the star’s surface radiates this energy into space.
Energy balance
102
the ball of neutrons created by the collapse of the iron core in a massive star supernova.
neutron star
103
The boundary of our observable universe, which is where the lookback time is equal to the age of the universe. Beyond this boundary in spacetime, we cannot see anything at all.
Cosmological Horizon
104
the building blocks of protons and neutrons
Quarks
105
the Carbon-Nitrogen-Oxygen cycle, a process of stellar nucleosynthesis in which stars on the Main Sequence fuse hydrogen into helium via a six-stage sequence of reactions.
CNO cycle
106
The chain of reactions by which low-mass stars (including the Sun) fuse hydrogen into helium.
Proton-Proton chain
107
The core again shrinks after helium core fusion ceases. Helium shell fusion begins around the inert carbon core beneath the hydrogen- fusing shell. The outer layers expand again, making the star into a double shell–fusion star. The star’s energy generation never reaches equilibrium during this time; instead, the star experiences a series of thermal pulses and ultimately expels its outer layers into space as a planetary nebula. The remaining “dead” stellar core is a white dwarf. What is this describing?
Death of a low mass star
108
the core left over from a low-mass star, supported against the crush of gravity by electron degeneracy pressure.
white dwarf
109
The era of the universe lasting from 10-10 second to 0.001 second after the Big Bang, during which subatomic particles were continually created and destroyed, and ending when matter annihilated antimatter.
Particle Era
110
The era of the universe lasting from about 0.001 second to about 3 minutes after the Big Bang, by the end of which virtually all of the neutrons and about one-seventh of the protons in the universe had fused into helium.
Era of nucleosynthesis
111
The era of the universe lasting from about 3 minutes to about 380,000 years after the Big Bang, during which matter in the universe was fully ionized and opaque to light. The cosmic background radiation was released at the end of this era.
Era of nuclei
112
The era of the universe lasting from about 500,000 years to about 1 billion years after the Big Bang, during which it was cool enough for neutral atoms to form.
Era of atoms
113
the explosive burning of helium in the case of a star of low mass that occurs when the core is so dense that the matter has become degenerate
Helium flash
114
The fundamental starting point for general relativity, which states that the effects of gravity are exactly equivalent to the effects of acceleration.
Equivalence Principle
115
The hot, compact corpses of low-mass stars, typically with a mass similar to that of the Sun compressed to a volume the size of Earth.
White dwarfs
116
The inseparable, four-dimensional combination of space and time.
Spacetime
117
The law stating that an object’s apparent brightness depends on its actual luminosity and inverse square of its distance from the observer. Apparent brightness = start fraction luminosity over 4 pi times distance squared end fraction.
Inverse square law for light
118
The layer of the Sun’s atmosphere below the corona; most of the Sun’s ultraviolet light is emitted from this region, in which the temperature is about 10,000 K.
Chromosphere
119
The magnification or distortion (into arcs, rings, or multiple images) of an image caused by light bending through a gravitational field, as predicted by Einstein’s general theory of relativity.
Gravitational Lensing
120
The name given to hypothetical tunnels through hyperspace that might connect two distant places in the universe.
Wormholes
121
The period of about 11 years over which the number of sunspots on the Sun rises and falls.
Sunspot Cycle
122
The point on a cluster’s H-R diagram where its stars turn off from the main sequence; the age of the cluster is equal to the main-sequence lifetime of stars at the main-sequence turnoff point.
Main-sequence turnoff point
123
The present era of the universe, which began with the formation of galaxies when the universe was about 1 billion years old.
Era of galaxies
124
the process by which matter gravitationally bound to a body, usually a star, fills its Roche lobe and becomes gravitationally bound to a second body, usually a compact object (white dwarf, neutron star or black hole), and is eventually accreted onto it.
mass exchange
125
The process by which photons gradually migrate from a hot region (such as the solar core) to a cooler region (such as the solar surface).
Radiative Diffusion
126
The process in which gravity causes an object to contract, thereby converting gravitational potential energy into thermal energy.
Gravitational Contraction
127
The prominent line of points (representing main-sequence stars) running from the upper left to the lower right on an H-R diagram.
Main Sequence
128
The redshift we see from distant galaxies, caused by the fact that expansion of the universe stretches all the photons within it to longer, redder wavelengths.
Cosmological Redshift
129
The relation, discovered by Henrietta Leavitt, that describes how the luminosity of a Cepheid variable star is related to the period between peaks in its brightness: the longer the Cepheid’s period, the more luminous the star. Also called the Cepheid period–luminosity relation.
Leavitt’s law
130
the remains of a supernova explosion
supernova remnant
131
the size of a black hole is characterized by its ___________ radius
Schwarzschild
132
The slowing of time that occurs in a gravitational field, as predicted by Einstein’s general theory of relativity.
Gravitational Time Dilation
133
the study of the overall structure and evolution of the universe.
Cosmology
134
The tenuous uppermost layer of the Sun’s atmosphere; most of the Sun’s x-rays are emitted from this region, in which the temperature is about 1
million K.
Corona
135
the theoretical thermal black-body radiation released outside a black hole's event horizon.
Hawking radiation
136
the time it has taken for the galaxy’s light to reach us.
Lookback time
137
The total power output of an object, usually measured in watts or in units of solar luminosities (LSun = 3.8 × 1026 watts).
Luminosity
138
The type of geometry in which the rules—such as that lines that begin parallel eventually meet—are those that hold on the surface of a sphere. Sum of triangle is more than 180°.
Positive (Spherical) Geometry
139
The type of geometry in which the rules—such as that two lines that begin parallel eventually diverge—are most easily visualized on a saddle-shaped surface.
Negative (Saddle-shaped) geometry
140
The very large and very bright stars that appear at the top of an H-R diagram.
Supergiants
141
The visible surface of the Sun, where the temperature averages just under 6000 K.
Photosphere
142
These high energy force carrier particles may exist if they are short lived. In a sense, they escape reality's notice.
virtual particles
143
This epoch was the period in the evolution of the early universe where universe was soup of particles, # of protons and neutrinos were the same till age 0.1 seconds. After 1 second, neutrinos ceased interacting with particles. Age of the universe was 10-4 to 15 seconds.
Lepton Epoch
144
True or false? A person moving by you at high speed will see exactly the same effects on you as you see on her.
TRUE
145
True or False? Time and space must be relative in much the same way that up and down are relative on Earth.
TRUE
146
Vaulted loops of hot gas that rise above the Sun’s surface and follow magnetic field lines.
Prominences
147
Waves, predicted by Einstein’s general theory of relativity, that are created by changes in a local gravitational field and cause distortions of spacetime as they propagate outward through the universe at the speed of light.
Gravitational Waves
148
Weakly interacting massive particle (WIMP), heavy, electromagnetically neutral subatomic particle that is hypothesized to make up most dark matter
WIMPs
149
What 2 classes by spin does the standard model divide particles into?
fermions and bosons
150
What are the 2 types of stars that have exhausted their core supplies of hydrogen for fusion and are undergoing other forms of fusion at a more rapid rate as they near the ends of their lives?
Giants and Supergiants
151
What 3 key features of the universe are explained through the hypothesis that the universe underwent a rapid and dramatic period of inflation?
(1) the density enhancements that led to galaxy formation
(2) the smoothness of the cosmic microwave background
(3) the “flat” geometry of the observable universe.
152
What 3 major types do galaxies come in?
Spiral, Elliptical, Irregular
153
What allows us to determine a galaxy’s distance from the speed at which it is moving away from us, which we can measure from the redshift of its spectrum?
Hubble's Law
154
What are fermions further subdivided into?
Quarks and Leptons
155
What are the 2 assumptions for the special theory of relativity that have been proven?
(1) The laws of nature are the same for everyone, and (2) the speed of light is the same for everyone.
156
What are the 2 types of balances that keep the sun shining?
1) Gravitational equilibrium
2) Energy Balance
157
What are the 3 basic properties of a black hole?
its mass, electric charge, and angular momentum.
158
What are the 3 groups we divide stars by mass?
Low mass stars, intermediate mass stars, high mass stars
159
what are the 3 most important properties of a particle?
mass, charge, and spin.
160
What are the 3 possible geometries for the spacetime curvature?
1. Flat geometry
2. Spherical (Positive) geometry
3. Saddle-shaped (Negative) geometry
161
What are the 4 fundamental forces?
gravity, electromagnetism, the weak force, and the strong force.
162
What arises from the curvature of spacetime?
Gravity
163
What can neutron stars in close binary systems accrete?
hydrogen-rich material from their companions, forming dense, hot accretion disks.
164
What caused the Sun to start shining 4 1/2 billion years ago, making the core hot enough to sustain nuclear fusion?
Gravitational Contraction
165
What causes spacetime to curve?
Mass
166
What causes the sunsot cucle?
It's tied to the Sun’s ever- changing magnetic field, which is created by the combination of convection and the Sun’s rotation pattern (faster at the equator than at the poles).
167
What determines the paths of freely moving masses?
Curvature of spacetime
168
What do Close binary systems consisting of two black holes emit?
gravitational waves that lead to mergers.
169
What do some stars fail to achieve?
a proper balance between the amount of fusion energy welling up from their cores and the amount of radiative energy emanating from their surfaces.
170
What does the big bang theory say about the Olbers' paradox?
the night sky is dark because the universe has a finite age, which means we can see only a finite number of stars in the sky.
171
What emit gravitational waves that cause the average orbital distance to decrease with time until the neutron stars merge?
Close binary systems consisting of 2 neutron stars
172
What happens in the instance that gravity overcomes degeneracy pressure?
the core collapses and the star explodes
173
What idea is the theory of relativity based on?
the idea that all motion is relative.
174
What is a star cluster's age equal to?
the hydrogen-fusion lifetime of the hottest, most luminous stars that remain on the main sequence.
175
What is the evidence for an accelerating expansion?
Observations of distant supernovae show that the expansion of the universe has been speeding up for the last several billion years.
176
What is the exchange particle for electromagnetism?
Photons
177
What kind of stars allow fusion to proceed more quickly and enabling fusion of heavier elements to take place?
Stars of greater mass because they have hotter core temperatures.
178
What method of measuring distances do we use for greater distances?
Standard candles
179
What might dark matter be made of?
could be ordinary (baryonic) matter in the form of dim stars or planetlike objects, but the amount of deuterium left over from the Big Bang and the patterns in the cosmic microwave background both indicate that ordinary matter adds up to only about one-sixth of the total amount of matter. The rest of the matter is hypothesized to be exotic (nonbaryonic) dark matter consisting of as- yet-undiscovered subatomic particles called WIMPs.
180
what might've formed protogalactic clouds and then galaxies from slight density enhancements in the early universe?
Dark matter
181
What observable evidence supports the idea that black holes really exist?
Some x-ray binaries include compact objects far too massive to be neutron stars, making it likely that they are black holes.
182
What principle says that a vacuum cannot be completely empty but must instead be filled with unobservable virtual particles that are constantly popping in and out of existence?
uncertainty principle
183
What scatters newly produced elements into space and leaving a neutron star or a black hole behind?
a supernova
184
What standard candle should be used at the most extreme distances in space?
White Dwarf Supernovae
185
what stars like the Sun become after they have exhausted their nuclear fuel
white dwarf
186
What studies can we use to know what is happening inside the sun?
Solar vibrations and solar neutrinos
187
What tells us how long it would have taken the universe to reach its present size if the expansion rate had never changed?
Inverse of Hubble's constant
188
What tells us that different observers can measure time, distance, and mass differently, even though everyone always agrees on the speed of light?
Special Relativity
189
What tells us that gravity arises from the curvature of spacetime and that the curvature arises from the presence of masses?
General relativity
190
what tells us that no material object can reach or exceed the speed of light (in a vacuum) and that E=mc^2?
Special Relativity
191
What the important standard candles?
Cepheid variable stars, white dwarf supernovae
192
when 2 particles interact bosons are exchanged between the 2 particles creating a force. implies that the exchange has to be asymmetrically
exchange particles
193
When does a supernova occur?
after fusion causes iron to pile up in the core of the high-mass star.
194
When one star in a close binary system begins to swell in size at the end of its main-sequence stage, what can transfer to its companion?
mass
195
Where are high mass stars located along the main sequence?
at the upper left
196
Where are Smaller mass stars located along the main sequence?
toward the lower right
197
Where do gamma-ray bursts come from?
unusually powerful supernova explosions that may create black holes.
198
Where do less common short gamma-ray bursts come from?
mergers of neutron stars in close binary systems.
199
Where has direct detection of gravitational waves come from?
from the instrument called LIGO
200
Where has indirect evidence for gravitational waves come from?
observing the orbital decay of binary neutron stars
201
why couldn't we use gravitational contraction to determine how old the sun is?
Studies of rocks and fossils had already suggested that Earth was far older than 25 million years
202
Why does a shrinking gas cloud heat up?
Because the gravitational potential energy of gas particles far from the center of the cloud is converted into thermal energy as the gas moves inward
203
Why is flat geometry evidence for dark energy?
According to Einstein’s general theory of relativity, the universe can be flat only if the total amount of mass-energy it contains is equal to the critical density, but measurements of the total amount of matter show that it represents only about 30% of the critical density. We therefore infer that about 70% of the total mass-energy is in the form of dark energy—the same amount implied by the supernova observations.
204
Stars with masses between and 2Msun and 8Msun?
intermediate mass stars
205
_______-mass stars never get hot enough to fuse carbon into heavier elements in their cores, and they end their lives by expelling their outer layers and leaving white dwarfs behind.
Low
206
________-mass stars live short but brilliant lives, ultimately dying in supernova explosions.
High
207
_________ appear to be distributed in gigantic chains and sheets that surround great voids.
Galaxies
208
_________ _________ acts as a thermostat that keeps the fusion rate steady.
gravitational equilibrium
209
__________-mass stars live shorter lives.
higher
210
A change in the direction in which the light is traveling.
Refraction
211
The point at which rays of light that were initially parallel (such as those from a distant star) converge.
focus (of a lens or mirror)
212
The amount of time during which light is collected to make a single image.
exposure time
213
The area of the primary mirror or lens that collects light in a telescope.
light-collecting area (of a telescope)
214
The angular resolution that a telescope could achieve if it were limited only by the interference of light waves; it is smaller (i.e., better angular resolution) for larger telescopes.
Diffraction limit
215
telescope that uses transparent glass lenses to collect and focus light
refracting telescope
216
telescope that uses a precisely curved primary mirror to gather light. Mirror reflects gathered light to a secondary mirror.
reflecting telescope
217
reflects light to a focus at a place where the eye can observe it through a hole in the primary mirror and sometimes through the side of the telescope.
Secondary mirror
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What are the 3 categories of observations with a telescope?
imaging, spectroscopy, and time monitoring.
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use diffraction grating to separate various color of light into spectra, which are then recorded with a detector.
Spectrographs
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stops us from seeing many stars from a big city
Light pollution
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What bends light in continually shifting patterns?
Turbulence of air in atmosphere
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A technique in which telescope mirrors flex rapidly to compensate for the bending of starlight caused by atmospheric turbulence.
Adaptive Optics
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What is the best atmosphere for a telescope?
dark, dry, calm, and high.
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Telescope that can observe visible light, infrared, and ultraviolet.
Hubble's telescope
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Telescope that collects radio waves reflected by primary mirror and sends then to the television; point toward cosmic radio sources that rise and set with Earth's rotation.
Radio telescope
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telescope that uses infrared light to detect celestial bodies; the higher you go in the atmosphere, the more infrared light becomes accessible.
Infrared telescopes
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What light does Earth's atmosphere almost completely absorb?
Ultraviolet
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Telescope that uses massive detectors to capture photons and determine the direction they came from.
Gamma-ray telescope
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These telescopes must be placed into space! Grazing Incidence Mirrors, x-rays merely graze their surfaces as the rays are deflected toward the focal plane.
X-ray telescopes
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The place where an image created by a lens or mirror is in focus.
Focal plane
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Particles such as electrons, protons, and atomic nuclei that zip through interstellar space at close to the speed of light.
Cosmic rays
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Waves, predicted by Einstein’s general theory of relativity, that are created by changes in a local gravitational field and cause distortions of spacetime as they propogate outward through the universe at the speed of light.
gravitational waves
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link 2 or more telescopes together to achieve the angular resolution of a much larger telescope.
Interferometry
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A type of fundamental particle that has extremely low mass and responds only to the weak force; neutrinos are leptons and come in three types— electron neutrinos, muon neutrinos, and tau neutrinos.
Neutrino
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A form of hydrogen in which the nucleus contains a proton and a neutron, rather than only a proton (as is the case for most hydrogen nuclei).
Deuterium
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The process by which photons gradually migrate from a hot region (such as the solar core) to a cooler region (such as the solar surface).
Radiative Diffusion
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emits bursts of ultraviolet light and x-rays along with charged particles moving at nearly the speed of light
Solar flares
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regions of the corona that barely show up in x-ray images; nearly devoid of hot corona gas.
Coronal Holes
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large #s of ejected highly energetic charged particles from the sun's corona.
Coronal Mass Ejections
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Describes luminosity and apparent brightness we could measure if we could detect photons across the entire electromagnetic spectrum
total luminosity and total apparent brightness.
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devised by Greek Astronomer Hipparchus; used to describe apparent brightness and luminosities of stars.
magnitude system
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describes how bright star appears in the sky.
Apparent Magnitude
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the apparent magnitude it would have if it were at a distance of 10 parsecs (32.6 ly) from Earth.
Absolute magnitude
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What color is the O spectral class of stars?
very blue
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What color is the B spectral class of stars?
blue
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What color is the A spectral class of stars?
white
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What color is the F spectral class of stars?
slightly yellow
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What color is the G spectral class of stars?
yellow
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What color is the K spectral class of stars?
orange
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What color is the M spectral class of stars?
red
250
What spectral class has the hottest stars?
class O
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What spectral class has the coolest stars?
class M
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A pair of stars that we can see distinctly as the stars orbit each other.
Visual Binary
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identified through observations of doppler shirts in its lines; one star orbits the other, it periodically moves towards us and away from us in its orbit, meaning its spectral lines will show alternating blueshifts and redshifts.
Spectroscopic binary
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2 sets of lines shifting back and forth; one set from each of the 2 stars in the system.
Double-lined spectroscopic binary
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a set of shifting lines from only one star because its companion is too dim to be detected.
Single-lined spectroscopic binary
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a pair of stars that orbit in the plane of our line of sight.
Eclipsing binary
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Prominent streak running from the upper left to the lower right on the H-R diagram
Main sequence
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in the upper right of H-R diagram; named that because they are very large in addition to being very bright.
supergiants
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Below the supergiants on the H-R diagram; somewhat smaller in radius and lower in luminosity.
giants
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stars near the lower left on the H-R diagram; are small in radius and appear white in color because of their high temp.
white dwarfs
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cluster found in the disk and hold young stars
Open clusters
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cluster found in the halo and have older stars
globular clusters
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stars born with less than about 2 solar mass of material
low mass stars
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stars born with masses between 2 and 8 solar masses.
intermediate stars
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stars born with mass greater than 8 solar masses
high mass stars
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What is the one element from which it is not possible to generate any kind of nuclear energy?
Iron
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neutrons are closely packed; supports neutron stars against the crush of gravity.
Neutron degeneracy pressure
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What does Einstein's theory say about binary systems where both objects are neutron stars?
such systems should radiate gravitational waves, and the energy lost in the way should cause the orbits of the 2 neutron stars to decay.
269
What are the properties of a black hole?
Mass, electric charge, and angular momentum
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stars that orbit in the same plane and include stars of all ages and masses,
Disk stars
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Stars that are randomly oriented orbits and are all old and low in mass.
Halo stars
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Consists of stars and dusty gas clouds that follow orderly, nearly circular orbits around the galactic center.
Disk component
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Includes both the halo and central bulge, generally has a rounded or elliptical shape, contains little cool gas and dust, and stars have orbits with many different inclinations.
halo component
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What is the distance chain order?
radar ranging, parallax, Cepheid variables, White dwarf supernovae, hubble's law
275
What 2 things about the universe is abosolute?
1) the laws of nature are the same for everyone
2) the speed of light is the same for everyone.
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The 3 motivations for inflation
1. horizon problem
2. flatness problem
3. structure formation
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Inflation fixes this problem because the universe expands so much that a small region that is in causal contact ends up being bigger than the observable universe.
horizon problem
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During inflation, the curvature of the universe neared flatness in the same way as inflating a balloon flattens out regions on its surface. If universe was completely curved, universe would have crashed.
flatness problem
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Inflation produces an extremely homogeneous Universe, but quantum fluctuations create fluctuations in density from place to place
structure formation problem
