SCIE Lecture Notes All Flashcards
(145 cards)
1
Q
what does the Cosmological Principle state about the universe on large scales?
A
universe is isotropic and homogenous
same in all directions (isotropic), made of same stuff (homogenous)
2
Q
at what scale do we observe the effects of teh Cosmological Principle?
A
150 Mpc
3
Q
what does the Cosmological Prinicple imply about the laws of physics?
A
laws of physics are the same everywhere
4
Q
what is the significance of quantum fluctuatuons in the early universe?
A
quantum fluctuations are caused slight over-dense and under-dense reagions, which influenced the structure of the universe
5
Q
how did baryons interact with areas of high density in the early universe?
A
baryons gravitationally collapsed into areas of high density
6
Q
what is the formula for measuring distance using redshift?
A
D = cz/Ho
7
Q
how is redshift measured?
A
by spectrum and using a spectrograph
8
Q
formula for redshift (z)
A
z = (delta wavelength) / (wavelength o)
9
Q
what percentage of total matter do galaxies make up?
A
5%
10
Q
what is the reason for the bias shape of galaxies?
A
galaxies trace the underlying dark matter
11
Q
what phenomenon describes the apparent stretching of galaxy groups along the line of sight?
A
Fingers of God
12
Q
what is redshift distortion?
A
refers to the apparent stretching of galaxy groups along the line of sight due to peculiar velocities
13
Q
what are the main structures observed in the universe?
A
voids, filaments, sheets/walls, clusters, groups and tendrils
14
Q
what do dark matter simulations help us understand?
A
help us simulate the universe starting with dark matter particles and allowing gravity to take control
15
Q
what does the observations that everything is moving away from us imply about the early universe?
A
all matter was condensed into a single point
16
Q
who proposed the idea that remnants of the early universe may be observable by radiation in 1931?
A
George Lemaitre
17
Q
what characterises plasma in the context of the universe?
A
characterised by a large number of charged particles
18
Q
what happens to atoms and molecules in a very hot gas during the early universe?
A
they can loose electrons, resulting in a plasma state
19
Q
what was the state of the universe immediately after the big bag?
A
hot dense state, existing in a plasma state where photons could not escape
20
Q
what occurs duing the process of recombination in the exapnding universe?
A
electrons recombine with protons as the universe coools down, allowing light to travel through
21
Q
what did Richard Tolaman state about the expansion of the universe in 1934?
A
he stated that the expansion would cause a cool black body spectrum and thermal spectrum
22
Q
what temperature is asscoaited with the CMB radiaiton accoring to Raloh Alpher and RObert Herman?
A
5 K
23
Q
what was teh Holmdel Horn’s initital purpose in NASAs communication efforts?
A
it was trying to bounce radio signals off balloons for communication
24
Q
what significant discovery was made by Robert Dicke and his heat at Princton regaring the CMB?
A
they accidentally detected a hiss corresponding to the thermmal background radtion about 4.2 K, leading to the first dedection of the CMB
25
what principle states that atoms cannot occupy the same space att the same time in the early universe?
exclusion principle
26
what can we learn about cosmology from the CMB?
we can learn about the grometry of teh universe, its fate, the mass-energy makeup, and large-scale structures
27
how does light behave in raltion to the geometry of the universe?
light follows the shortest path, which can be hyperbolic of Euclidean depending on the curvature of space
28
what does the CMB reveal about the large-scale structure of the Universe?
distribution and composition of matter in the universe
29
who measured the size of galxy and the postion of our solar system in 1920?
Harlow Shapley
30
what methods did Harlow Shapley use to measure distances to nearby globular clusters?
star parallax and standard candles
31
how did Harlow Shapley estimate distances to distant gobular clusters?
by assuming similar luminosity
32
what assumption did Harlow Shapley make to estimate the distance to the Galactic centre?
he assumed a spherical distribution of globular clusters centering around the Galactic center
33
what significant discovery did Edwin Hubble make in 1924?
discovered that the universe goes beyond the Milky Way
34
what did Hubble prove about nebulae in 1924?
nebulae are galaxies like the Milky Way
35
what is Hubbles Law, discovered in 1929?
galaxy redshift increases with distance, indicating that the universe is exapnding
36
what classifification system did Edwin Hubble devise in 1936?
Hubble Sequence for galaxy morphology classification
37
what happens to the observed frequencies of objects moving towards us?
they are blue-shifted = higher frequencies and shorter wavelengths
38
what does the equtions V = Ho d represent?
Hubble's Law, where recession velocity (V) is proportional to distance (d)
39
what does the expansion of the universe imply about the space between objects?
the space is expanding
40
what is the relationship between distance and speed of recession in an expanding universe?
the speed of recession is proportional to distance; the further and object is, the faster it is moving away
41
what did observations suggest about the acceleration of the universe?
the comic expansion is accelerating
42
what concept did George Lemaitre propse regarding the origin of the universe?
suggested that the universe might have originated from a primeval cosmic egg that exploded
43
what constant did Einstein introduce in his equations, and what does it explain?
introduced a constant to make the universe static, which explains dark energy that is causing the expansion of the universe to accelerate
44
what evidence supports the big bang theory?
the age of the universe, age distribution of galaxies, heavy element absundance, CMB
45
what does the term dark energy refer to?
refers to the unknown form of energy causing the accelerated expansion of the universe
46
what does the black solid line in the context of the universe expansion represent?
predication for an accelerating universe
47
what does the observtion of over 50 supernovae suggest about the universe?
cosmic expansion is accelerating
48
how is a second defined in modern times?
a second is defined as the time that elapses during 9.192x10^9 cycles of the radiation produced by the transition between two energy levels of cesium
49
what historical method was used to define a second?
defined as 1 solar say divided by 86400
50
what is the definition of a meter based on the speed of light?
the distance light travels in a vacuum in 1/299792458.6 seconds
51
what is the comic distance ladder?
a succession of methods used to determine the distance to celestrial objects, where no single technique can measure all the distances encountered in astronomy
52
how is the distance to the sun measured?
measuing the distances to other planets first and applying Newtonian physicals, with 1 AU representing the average distance from Earth to the Sun
53
what is parallax and how is it used to measure distances to nearby stars?
the apparent angular displacment of nearby stars compared to distant stars, used to measure distances up to 400 light years based on the Earth's movement relative to the Sun
54
what is the maximum distance Gaia can measure to stars?
up to 30,000 light years
55
what is the principle behind standard candles in astronomy?
unitilse the inverse square law, where luminosity decreases by a factor of the square distance
56
what is the significances of the H-R diagram in measuring stellar luminosity?
plots stars based on their temperature and luminosity, allowing luminosity to be determined by measured flux and distance
57
what are Cepheid Variables and their importance in astronomy?
CV are stars that expand and contract continiously, used as standard candles where brighter variables have longer periods, linking luminosity to pulsating period
58
what are type la supernovaae and their role as standard candles?
extremely bright events, their light curve powered by radioactive decay, allowing distance measurements through Phillips' relation
59
what is Hubble's Law?
the universe is expanding, and the expasnsion rate can be measured by the receding velocity or redshift of distant objects
60
what is the significance of graviational waves from binary meregers as Standard Sirens?
provide independent distance measurments without needing distance ladders, by require accurate sky direction and inclination angle measurments
61
what is the relationships between luminoisty and pulsating period in Cepheid Variables?
longer pulsating periods = brighter intrinsic luminosity
62
what is the role of EM counterparts in graviations wave measurments?
electromaganetic counterparts are important for providing sky direction in gravitational wave measurments
63
what is the maximum distance for observing type la supernovae?
1 billion light years
64
how does the inverse square law relate to luminosity and distance?
luminosity decreases as teh distance from the source increases by the square of the distance
65
what is teh significance of collecting spectra in determining stellar properties?
to determine temperature and other properties of stars, which can then be plotted on the HR diagram
66
what is the method used to measure distances to objects in our solar system?
radar beams bouncing off objects, though the SUn cannot be measured this way directly
67
what is the importance of calibrating methods in the Cosmic Distance Ladder?
as measurments of more distant ibject rely on accurate measurements of closer objects
68
what does luminosity refer to in the conext of standard candles?
intrinsic brightness of an astronomical object, which can be inferred from its observed brightness and distance
69
what is the significance of teh 13 billion light years in Hubble's Law?
respresents the distance scale at which Hubble's Law applies, indicating how far we can observe the universes expansion
70
what are the main characteristics of spiral galaxies?
- fast-ratating disk
- central stellar bulge
- less crowded regions
- young, blue stars in spiral arms
- old, red stars in the bulge
71
what defines elliptical galaxies?
- ellipsodial shape and a smooth, bright profile
- found in galaxy clusters
- mostly old red stars
- little gas and dust
72
what is the significance of the Canis Major Dwarf Galaxy in relation to the Milky Way?
tidally disrupted as it is attracted to the central regions of the Milky Way, leading to its destruction
73
how can the motion of galaxies be measured?
blue/red shift, emission lines
74
what is the hierarchical model for galaxy formation?
gas and dust collapse due to gravity to form proto-galaxies
75
how does dark matter interact with gas during galaxy formation?
gas can cool and loses kinetic energy by emitting ER, flow towards the centre of dark matter halos, dark matter cannot radiate and maintains kinetic motion
76
what occurs during teh disk formation of spiral galaxies?
gas flows towards centre of dark matter halo, its angular momentum is conserved, leads to compression, increases spin speed, and leads to the formation of a flat central disk
77
what is the density of wave theory in relation to spiral arms?
stars and gases are slowed and compressed by density waves, triggering the formation of stars and nebulae
78
what characterises a starburst galaxy?
Eg. Cigar Galaxy
chracterised by region of high star formation due to the merging of gas and dust from spiral galaxies
79
what is the role of an active galatic nucleus (AGN)?
formed from the merger of two galxies, accretion onto a supermassive black hole, produced ER and powerful jets, suppressing star formation
80
what happens to a galaxy after star formation acitivty ceases?
galaxy becomes dominated by long-lived yellowish stars and may eventually become dormant with little gas and stars
81
what evidence supports the merger model of galaxy formation?
computer simulations, prevalence of elliptical galaxies in clustrs, many elliptical galaxies host AGNs and exhibit redder stars
82
what are the main differences between the Hubble and Webb telescopes?
Hubble: optical, 2.4 m diameter
Webb: infared, 6.5 m diameter primary mirror always in earth's shadow
83
what is the signifance of the merging antennae and mice galaxies?
processes of galaxy interaction and star formation triggered by gravitaitonal interactions
84
what happens to gas during the formation of elliptical galaxies?
form from the merging of gas and dust from spiral galaxies, regions of high star formation known as starbursts
85
what is the relationship between AGNs and star formation?
ADN radiation suppresses star formation by dissociating and ionsising cold hydrogen and applying raadiation pressure that limits the inflow of new gas
86
how does the roational velocity of gas affect the formation of a spural galaxy's disk?
as diameter of gas strcuture increases = rotational velocity increases, results in centrifugal forces that help settle gas into a disk
87
what is the observable effect of density waves in spiral galaxies?
density waves create visable galactitic traffic jams where stars and gases are compressed, leading to star formation in high density regions
88
what is the expected outcome for black holes in galaxies over time?
black holes eventually run out of fuel, become dormant and leading to a galaxy dominated by old stars, little star formation
89
what is the role of EMR in teh cooling of gas in galaxy formation?
EMR allows gas to cool and lose kinetic energy,m facilitating its flow towards teh centere of dark matter halos
90
how do elliptical galaxies differ in structures compared to spiral galaxies?
lack internal structure seen in spiral galaxies, smooth brigness profile and little star formation
91
what is the typical size range of galaxies?
10^6 - 10^14 stars
92
what distinguishes dwards from giant galaxies?
dwards contain milllions of stars, giant galaxies can have up to 100,000
93
what is the diameter range of galaxies?
few thousands - few million light years
94
what is the typical separation distance between galaxies?
few Mpc
95
what are the four main types of galaxies classified in the Hubble Sequence?
elliptical, spiral, lenticular, irregular
96
lenticular galaxy
large bulge in the middle, large disk and no spiral arms
97
how does Hubble's classification of galaxies relate to their evolutionary direction?
classification is empirical and does not represent the direction of galaxy evolution
98
what is the classification of the MW?
SBbc, central bar and loose spiral arms
99
what is an open cluster?
group of hundreds to thousands of stars formed from a giant molecular cloud, found concentrated on the disk of a galaxy
100
what is a globular cluster?
spherical collection of hundreds of thousands to millions of stars that remain gravitationally bound and are typically very old
101
what is the significance of spiral arms?
dense regions, star forming area, young blue stars
102
what is measured in roation curves of galaxies?
rotation speed of gas and stars from distnce from the centre of galaxy
103
what is teh rotation curve problem?
the measured roation curve is flat, which is incompatible with predictions from Keplerian orbits
104
what percetage of the universe is made up of dark matter?
25%
105
what is the relationship between flux and distance?
measured flux is proportional to luminosity divided by the square of the distance
106
what are apparent luminosity and intrinsic luminosity?
apparent luminocity = brightness of a star as seen from Earth
intrinsic luminocity is actual energy output of star
107
what is the order of the stretch of spacetime produced by gravitational waves from stellar mass black hole mergers at Earth's location?
10^-20 meters
108
what was the first indirect hint of GW?
Hulse-Taylor pulsar, involved measuring periastron
109
how do bar detectors detect GW?
if the GW frequency matces the resonant frequency of the cylinder, it will star oscillating
110
what are resonant detectors?
eg bar detectors, detect minimal vibratings, using black strips and operating at low temps
111
what types of noise can interfere with GW detection?
seismic vibrations, thermal noise, quantum noise
112
what is the significance of the arm length in ground-based gravitational wave detectors?
longer arm length = increase sensitivity
113
how does lasar pwoer affect noise in GW detectors?
increased lasar power = reduced shot noise - less noise in system
114
what is the function of a Michelson interferometer in GW detections?
measures small length changes by allowing half the light to pass through and reflecting the other half
115
what is the raltionship between the length of the L-shaped tubes in a Michelson infermoneter and distance measurment?
larger the length = finer the distance measurment
116
what is the maximum sensitivity direction for a gravitational wave detector's antenna pattern?
sensitivity is maximum for signals traveling vertically to the detector's plane
117
what s the minimum sensitivity direction for a gravitational wave detector's antenna pattern?
45 degrees
118
why is a single detector insufficient for localizing the source of gravitational waves?
a single detector cannot localize the source; at least three detectors are needed for triangulation
119
what factors are involved in the method of triangulation for gravitational wave detection?
triangulation depends on time of arrival differences, amplitude ratios, and phase lags
120
what is stochastic background noise?
noise that can interfere with the detection of GW, including thermal and quantum noise
121
what is the frequency range in which ground-based detectors are sensitive?
10-1000 Hz
122
what challenges do ground-based detectors face in detecting gravitational waves?
various noises including seismic, Newtonian, thermal, and quantum noise
123
whats the relationship between matter and spacetime?
matter tells spacetime how to curve, and spacetime tells matter how to move
124
how does energy density affect spacetime curvature?
higher the energy (mass) density, the larger the curvature
125
what causes GW waves?
by oscillations and events such as neutron stars revolving around each other
126
what are the conditions under which a perfectly spherical body produces gravitational waves?
perfectly spherical body rotating around its axis will not produce gravitational waves
127
BBH
binary black hole mergers
128
what are the different types of mergers that produce gravitational waves?
BBH (binary black hole), NSBH (neutron star-black hole), BNS (binary neutron star), and sub-solar mass mergers
129
what is the frequency range for Compact Binary Coalescence (CBC) signals?
10 Hz to 4000 Hz
130
what are the polarization modes of gravitational waves?
gravitational waves deform objects in two ways: 45 degrees to the axis (H cross) and 90 degrees parallel (H plus
131
what is the mass range for intermediate mass black hole binaries
100 to 100,000 solar masses (Mo)
132
what is the frequency range for supermassive black hole binaries?
10^-3 to 0.1 Hz
133
what is the significance of stochastic backgrounds in gravitational waves?
constant background signals that can be cosmological or astrophysical in origin
134
what sources contribute to the cosmological stochastic background?
inflation, phase transitions, and cosmic strings, with a frequency range of 10^-18 to 1 Hz
135
what are continious gravitational waves?
are steady, periodic signals from non-axisymmetric rotating objects
136
how do neutron stars differ in their gravitational wave emissions?
not spherical in shape can emit continuous gravitational waves due to their non-axisymmetric rotation
137
how does acceleration relate to mass in the context of gravity?
acceleration is inversely proportional to its mass, meaning objects fall at the same rate regardless of their mass
138
what does Newton's Laws of Gravitation state about space?
space exists in an absolute and rigid framework, independent of matter
139
what concept did Gauss challenge regarding geometry?
challenged the idea of Euclidean geometry by measuring distances and angles of shapes across space
140
what is a geodesic?
the shortest distance between two points
141
what is time dilation in the context of gravity?
time moves more slowly in high gravitational fields
142
what phenomenon occurs when light passes close to a massive object?
graviational lensing, causes light to bend
143
what experiment tested Einstein's prediction of gravitational lensing?
Eddington ested this by observing the bending of star light around the sun during a total solar eclipse in 1919
144
what is the effect of moving close to the speed of light on an object's movement?
an object moves more slowly as it approaches the speed of light
145
what is one method of detecting GW?
mergering neutron stars and black holes
