ASTR 123 module 7-8 quiz
Roughly what percent of the mass and energy contents of the universe is made up of ordinary (atomic) matter? a. 5 percent b. 10 percent c. 50 percent d. 95 percent e. astronomers have no way of estimating this percentage
a. 5 percent
To predict whether a star will ultimately become a black hole, what is the key property of the star we should look at? a. mass b. surface temperature c. color d. distance e. Diameter
a. mass
A gravitational lens is formed by a. mass between the source and earth b. a lens the size of a galaxy c. mass behind the source d. gravitational waves e. light redshifted by a black hole
a. mass between the source and earth
Spacetime effects like time dilation are only noticeable when a. objects move close to the speed of light b. we have proper telescopes c. events in spacetime are connected by light beams d. very massive objects are involved e. we are within a black hole's event horizon
a. objects move close to the speed of light
The three observational pillars of cosmology are the expanding universe, big bang nucleosyntheses, and a. the cosmic microwave background b. the age of globular cluster stars c. the rate of Type II supernovae d. the number of primordial black holes e. x-ray emission from black hole accretion disks
a. the cosmic microwave background
The speed that gravitational waves travel is a. the speed of light b. one half the speed of light c. the speed of sound in empty space d. dependent on the black hole mass e. twice the speed of light
a. the speed of light
Why did Einstein introduce the cosmological constant into the equations of his General Theory of Relativity when describing the universe? a. Einstein did not realize that black holes would exist at the centers of galaxies and pull everything into them b. Einstein's equations required the universe to expand or contract; he could not imagine or accept it doing either one, so he put a factor in to stop it from moving c. Einstein talked to Hubble and learned about Hubble's observations of the expanding universe, which made him so uncomfortable that he decided to change his equations d. Einstein had a hunch that the universe was accelerating (speeding up its expansion) back in 1918 and so introduced the constant into his equations to describe that
b. Einstein's equations required the universe to expand or contract; he could not imagine or accept it doing either one, so he put a factor in to stop it from moving
Einstein suggested that the regular change (advance) in the perihelion of the planet Mercury could be explained by: a. the presence of a planet inside the orbit of Mercury, whose gravity influenced Mercury b. a distortion in spacetime caused by the gravity of the Sun c. the pull of a small black hole that orbits our Sun so closely that we are not able to see it d. the presence of a strong magnetic field in the Sun, which causes huge outburst of material
b. a distortion in spacetime caused by the gravity of the Sun
When laser beams in an interferometer combine a. the resulting light only gets brighter b. an interference pattern of bright and dark light is formed c. the resulting light travels at twice the speed of light d. the increased laser power melts the camera e. the photons are destroyed
b. an interference pattern of bright and dark light is formed
General Relativity predicts that light passing near a massive object like the sun will a. be spread into a spectrum of wavelengths b. appear bent when observed from Earth c. be the same as always d. make the sun's mass exceed 1.4 solar masses e. be reflected back
b. appear bent when observed from Earth
After traveling 140 million light years from the 170817 neutron star merger, gravitational waves and gamma rays a. annihilated each other to produce a gamma-ray burst b. arrived at earth at almost exactly the same time c. combined to produce heavy elements d. were assumed to have been produced, but were not observed e. arrived at earth 1.4 years apart
b. arrived at earth at almost exactly the same time
Today, we believe that only a small number of elements were actually formed during the Big Bang. Which of the following was NOT one of these: a. hydrogen b. carbon c. deuterium d. helium
b. carbon
f the universe consisted only of matter and its density were equal to critical, the universe would a. continue expanding, then slow down and contract, ending in a "big crunch" b. continue expanding, eventually slowing down to zero c. continue expanding, eventually speeding up d. continue expanding at a reduced rate e. not expand at all
b. continue expanding, eventually slowing down to zero
When the age of the universe was about 10 seconds, it had cooled sufficiently for neutrons and protons to bind together and form the key nuclear species which allows production of helium to proceed. This key nucleus is called a. hydrogen b. deuterium c. lithium d. a quark e. carbon-6
b. deuterium
Current measurements of the Hubble constant H0 a. all agree on a single value b. disagree depending on the method used c. all use Type Ia supernovae as standard candles d. indicate the universe will someday contract to a single point e. are meaningless
b. disagree depending on the method used
Based on cosmic microwave background (CMB) data, astronomers now conclude that the average density of the universe is a. less than the critical density b. exactly equal to the critical density c. more than the critical density d. essentially equal to zero e. so great that the universe will experience a "big crunch" before the Sun becomes a red giant
b. exactly equal to the critical density
How does a period of extremely fast inflation very early in the history of the universe explain the observation that the geometry of the universe looks flat (not curved) to us? a. during inflation a lot of the mass drained out of the universe, leaving its gravity much weaker b. inflation increased the size of the universe so much that the resulting universe looks flat from any point of view c. inflation led to the production of so much dark matter that the universe got pulled into the shape of a black hole d. inflation caused the temperature of different parts of the universe that can't see each other still be the same e. The universe is actually highly curved and not flat
b. inflation increased the size of the universe so much that the resulting universe looks flat from any point of view
After a star collapses to form a black hole, the only information we can measure is a. the length of its "hair" b. its mass and spin c. the Hawking radiation d. its explosion probability e. whatever we want from inside the event horizon
b. its mass and spin
Modern particle accelerators are able to recreate some conditions of the early universe because a. of the vacuum used in the accelerator beam pipes b. of the high energy of the particles in the beams c. because of the large gravity of the earth d. they accelerate dark matter particles e. they produce primordial black holes
b. of the high energy of the particles in the beams
Galaxies that we see as they were 11 billion years ago or more, as compared to galaxies today, are generally: a. bluer and smaller b. redder and smaller c. redder and larger d. bluer and larger e. pretty much the same
b. redder and smaller
The "horizon problem" is illustrated by what observation of the cosmic microwave background (CMB)? a. that the microwaves should not have been able to reach us b. that the size of the universe represented by the CMB seems to extend beyond the visible horizon c. that the temperature of disconnected regions is almost exactly the same d. that large scale structure doesn't seem to be implied from the CMB e. that the CMB is analogous to a black hole horizon
b. that the size of the universe represented by the CMB seems to extend beyond the visible horizon c. that the temperature of disconnected regions is almost exactly the same
When astronauts aboard the International Space Station (ISS) in space let go of an orange, it just floats there. Why is that? a. the ISS is so far from the Earth, the gravity there is essentially zero b. the ISS is falling around the Earth, and in free fall, things feel no weight c. spacetime is so different aboard the ISS, that time stops, and so nothing can fall d. the law of gravity only works on the Earth, it doesn't work in space
b. the ISS is falling around the Earth, and in free fall, things feel no weight
Recent observations indicate that the universe is expanding faster today than it was a few billion years ago (that, in other words, the expansion of the universe is accelerating.) What kind of observations have led astronomers to this surprising conclusion? a. the measurements of cepheid variables in the galaxies of the Local Group b. the measurement of galaxy distances using Type Ia supernovae c. the discovery of large amounts of dark matter in the halo of the Milky Way d. the measurements of the amount of deuterium in the universe
b. the measurement of galaxy distances using Type Ia supernovae
The first time that astronomers observed both gravitational waves and electromagnetic waves from the same event, what they were observing was: a. a supernova explosion in one of the closest galaxies to us b. the merger of two neutron stars c. a binary star system where a giant star is overloading a white dwarf with too much material d. the merger of two black holes with masses dozens of times the mass of our Sun e. the collapse of an entire cluster of stars into one big black hole
b. the merger of two neutron stars
Observations of the afterglow of the 170817 binary neutron star merger revealed a. nothing; all of the light was trapped within the event horizon b. the presence of newly created heavy elements c. the presence of helium d. annihilations with dark matter e. a black hole
b. the presence of newly created heavy elements
The main postulate of special relativity is that a. the speed of gravity is zero b. the speed of light is an absolute constant c. cosmic rays should be able to reach the earth d. space and time should be discarded e. the speed of thought is nonexistent in Wil 100
b. the speed of light is an absolute constant
In the observation of galaxies, astronomers refer to look-back time, which means a. the glory days of astronomy b. the time it took for the observed light from a galaxy to reach us c. the current distance to a galaxy divided by c d. the time required to take a good spectral image of the galaxy e. Thursdays
b. the time it took for the observed light from a galaxy to reach us
The reason nucleosynthesis stopped when the age of the universe was about 3 minutes was a. because all the elements had been created at that point b. the universe was cooling too fast to produce elements beyond helium c. the universe was cooling too fast to produce elements beyond carbon d. the universe began re-heating, breaking apart any new nuclei e. it didn't stop, but began accelerating
b. the universe was cooling too fast to produce elements beyond helium
The observed cosmic microwave background (CMB) is extremely uniform. What is the significance of the small deviations from uniformity which show up as red or blue regions in the CMB images? a. they are known experimental errors b. they seed the large scale structure we observe today c. they turn into supermassive black holes d. they became the Virgo cluster of galaxies
b. they seed the large scale structure we observe today
If our Sun were to become a black hole, the radius of its event horizon would be about a. 1 inch b. 2 Mpc c. 3 kilometers d. 4 AU e. 5 light years
c. 3 kilometers
The object(s) created by the merger of two black holes is a. a neutron star b. a pair of black holes with slightly lower mass c. a single black hole with mass slightly lower than the sum of the merging ones d. a single black hole with mass equal to the sum of the merging ones e. a supernova
c. a single black hole with mass slightly lower than the sum of the merging ones
Which of the following statements about dark matter is FALSE: a. it is observed to be a major part of the Milky Way b. it is observed to be present in other groups of galaxies c. astronomers have a pretty good idea what the dark matter is made of d. we can detect its gravity, even though we can't see it e. it may make up even more of the universe that the matter we can see
c. astronomers have a pretty good idea what the dark matter is made of
According to the Cosmological Principle, the universe a. has no beginning and no end b. cannot be understood by the use of scientific observations alone c. is isotropic and homogeneous over large distances d. consists only of galaxies that are exactly like the Milky Way e. has all the galaxies arranged in groups about the size of our Local Group
c. is isotropic and homogeneous over large distances
Special relativity gives a "speed limit", meaning that a. time slows down in rockets b. elliptical galaxies have smaller redshifts c. objects cannot move faster than the speed of light d. vehicles in Bern, Switzerland move too fast e. Einstein did not watch Star Trek
c. objects cannot move faster than the speed of light
Merging black holes can be observed a. only at night b. by their radio wave emissions c. only by their gravitational wave emission d. by radio and gravitational wave emissions e. by their x-ray and gravitational wave emissions
c. only by their gravitational wave emission
How do astronomers currently think the amount of detectable (observable) matter in the universe compares to the amount of dark matter? a. the amount of detectable matter is about equal to the amount of dark matter b. the amount of detectable matter is far greater than the amount of dark matter c. the amount of detectable matter is about 1/5th the amount of dark matter d. the amount of detectable matter is about 1% the amount of dark matter
c. the amount of detectable matter is about 1/5th the amount of dark matter
With enormous effort, a team of astronomers manages to collect enough light from a galaxy far, far away to produce a spectrum. That spectrum has lines from the elements carbon, silicon, and sulfur. This tells the team that a. the galaxy must be closer to us than 1 billion light years b. the galaxy must contain a quasar c. the galaxy must have had an entire generation of stars that was born, lived, and died d. the galaxy must be a massive elliptical galaxy
c. the galaxy must have had an entire generation of stars that was born, lived, and died
In the discovery of gravitational waves by LIGO in 2015, the waves came from a. the collapse of a nearby star into a white dwarf b. a supernova explosion in a nearby galaxy c. the merger of two black holes d. the rapid motion of three hot Jupiter planets around a nearby star
c. the merger of two black holes
In measuring the speed of stars orbiting on the outer edge of a galaxy, the expectation without dark matter is that a. the speed is the same as stars near the central bulge b. the speed increases as the star is further from the galactic center c. the speed decreases as the star is further from the galactic center d. the speed approaches c e. the speed undergoes a chirping evolution
c. the speed decreases as the star is further from the galactic center
A galaxy observed at redshift of z=4 has a prominent hydrogen spectral line. If this same spectral line has a wavelength of 100 nm when observed from hydrogen in a lab on earth, its observed wavelength from the galaxy is a. 20 nm b. 100 nm c. 200 nm d. 500 nm e. 1000 nm
d. 500 nm
According to the general theory of relativity, the presence of mass a. causes motion at the speed of light squared b. is equivalent to the presence of light c. causes curved paths to straighten out until they are exactly straight lines d. causes a curvature (or warping) of spacetime e. will cause a black hole to form, unless there is motion
d. causes a curvature (or warping) of spacetime
Where in space did the expansion of the universe begin? a. at the center of the Milky Way Galaxy; that's why all the other galaxies are moving away from us b. near the center of the Virgo Supercluster of Galaxies c. at a point so far away that only our largest telescopes can show us glimpses of it d. everywhere at once e. nowhere at all; new observations show that the universe is not expanding after all
d. everywhere at once
Measurements of the cosmic microwave background provide strong evidence that the overall geometry of space is a. trapezoidal b. spherical, or positive curvature c. hyperbolic, or negative curvature d. flat, or zero curvature e. circular
d. flat, or zero curvature
What do the surveys of the three-dimensional distribution of groups of galaxies reveal about how groups and clusters of galaxies are organized? a. galaxy groups are distributed completely evenly -- there is typically the same amount of space between them -- and so there is no structure evident b. galaxy groups make a huge spiral structure that resembles the Milky Way (but is much bigger) c. galaxy groups are organized into huge spherical "lumps" with concentric rings of groups of galaxies around each lump d. galaxy groups are organized into huge filaments with great voids between them e. astronomers cannot get any sense with our present-day instruments of how groups of galaxies are distributed on the large scale
d. galaxy groups are organized into huge filaments with great voids between them
What is a key reason that gravitational waves are so much harder to detect than electromagnetic waves? a. gravitational waves don't create any kind of disturbance the way electromagnetic waves do b. gravitational waves are so strong, they really shake our detectors, making measurements difficult c. gravitational waves get all mixed up with sound waves in the Earth's atmosphere, and are therefore hard to distinguish from all the sound d. gravitational waves are much weaker than electromagnetic waves, and therefore require very, very precise equipment to detect e. because the GW scientists are incompetent
d. gravitational waves are much weaker than electromagnetic waves, and therefore require very, very precise equipment to detect
Which of the following does NOT happen when two galaxies collide? a. large interstellar gas clouds collide b. the rate of star formation increases c. the shape of the galaxy is often changed d. many of the stars in one galaxy collide with the stars in the other e. a smaller galaxy may wind up inside a larger one
d. many of the stars in one galaxy collide with the stars in the other
We now know that most heavy elements such as gold are produced in a. factories in China b. supernova explosions of massive stars c. black hole mergers d. neutron star mergers e. white dwarf mergers
d. neutron star mergers
Which of the following did NOT happen during the first few minutes after the Big Bang? a. temperatures throughout the universe were hotter than the cores of stars are today b. two or three of the simplest elements fused together c. energy was converted to matter d. some very massive early stars formed e. matter and antimatter collided and turned into energy
d. some very massive early stars formed
Why do widely separated galaxies move apart? (Why do we have Hubble's law)? a. gravity is a repulsive force, once you get outside the Milky Way Galaxy b. each galaxy has net charge on it, and they repel by the laws of electricity c. supernova explosions happen more frequently on one side of each galaxy, giving the entire galaxy a push that moves it away from its neighbors d. space itself is stretching, and this stretching carries the galaxies away from each other
d. space itself is stretching, and this stretching carries the galaxies away from each other
When scientists say that "black holes have no hair", what do they mean? a. that the event horizon of a black hole is very smooth and does not have parts that jut out b. that if you threw something toward a black hole (a furry animal, say) it would quickly be ripped apart into smaller pieces c. that time near a black hole slows down so much our hair would not grow at a normal rate d. that once a black hole forms, very little information can be extracted from it about the material that is now inside e. no one knows what this means; regular people are not meant to figure out some of the weird things physicists say about black holes
d. that once a black hole forms, very little information can be extracted from it about the material that is now inside
The region around a black hole where everything is trapped, and nothing can get out to interact with the rest of the universe, is called a. the singularity b. the neutron star radius c. the gravitational redshift zone d. the event horizon e. television
d. the event horizon
The redshift observed in the light emitted by distant galaxies is due to a. the Doppler shift of the galaxies moving away from us through a fixed space b. the Doppler shift of the galaxies moving towards us through a fixed space c. the gravitational redshift of the galaxies' immense mass d. the expansion of space e. radio-bright quasars
d. the expansion of space
Which of the following does not represent evidence for dark matter? a. the rotation curves of stars moving around galaxies b. the large scale structure of galaxies and galaxy clusters c. analyzing the mass of gravitational lenses d. the fusion of hydrogen in stellar cores e. merging galaxy clusters
d. the fusion of hydrogen in stellar cores
The model of the universe that involves an enormous increase of size during a very short time in the early universe is called: a. the flat universe model b. the oscillating universe model c. the primeval atom model d. the inflationary universe model e. the cosmic burp model
d. the inflationary universe model
Which of the following does not represent evidence for dark matter? a. the rotation curves of stars moving around galaxies b. the large scale structure of galaxies and galaxy clusters c. analyzing the mass of gravitational lenses d. the rate of cosmic ray showers e. merging galaxy clusters such as the "bullet cluster"
d. the rate of cosmic ray showers
What happened when the age of the universe was 380,000 years which allows us to observe the cosmic microwave background? a. ancient civilizations developed microwave ovens b. the formation of the first stars c. the formation of the first galaxies d. the universe cooled sufficiently to allow neutral hydrogen to form e. the universe cooled sufficiently to allow deuterium to form
d. the universe cooled sufficiently to allow neutral hydrogen to form
The location of the 170817 neutron star merger was first determined using a. radio telescopes b. texts by ancient Chinese astronomers c. the iterative guess method d. three gravitational wave detectors e. the earth's rotation
d. three gravitational wave detectors
According to General Relativity, in a freely falling reference frame, light a. follows a curved path b. passes through a gravitational lens c. moves slower than c d. travels in a straight line e. moves faster than c
d. travels in a straight line
For the first generation of stars formed in the early universe, their composition a. included a lot of carbon and oxygen b. is essentially identical to our sun c. was primarily neutrons d. was almost entirely hydrogen
d. was almost entirely hydrogen
In the 2015 gravitational wave discovery event, the two black holes a. were supermassive b. combined to form a neutron star c. were each about 1 solar mass d. were each about 30 solar masses e. never merged
d. were each about 30 solar masses
When do astronomers now think that the "dark energy" began to accelerate the expansion of the universe? a. right after the Big Bang (after the first three minutes or so) b. a few million years after the Big Bang c. several billion years after the Big Bang d. within about a billion years of the present time
d. within about a billion years of the present time
The 170817 event demonstrated that neutron star mergers a. produce gamma ray bursts b. produce gravitational waves c. produce most of the heavy elements on earth d. produce kilonova afterglows e. all of the above
e. all of the above
A student shines a flashlight out the window of a very fast rocket. If the normal speed of light is c, then a. if she shines it forward, the light travels a bit faster than c b. if she shines it backwards, the light travels a bit slower than c c. if she shines it forward, the light travels a bit slower than c d. if she shines it backwards, the light travels a bit faster than c e. the light always travels at speed c
e. the light always travels at speed c
