Astronomy Exam 3: HW and TopHat
an object from which even light cannot escape.
A black hole is described as a very massive neutron star. an object from which even light cannot escape. a distortion in spacetime. a star that has run out of fuel.
70 Mpc
A galaxy is observed to moving away from us at a velocity of 14,000 km/s. How far away must it be?
25%
According to the Big Bang Theory, how much of the mass in the Universe should have been converted into helium right after the big bang occurred? 70% 8% 25% 5%
acceleration.
According to the principle of equivalence, gravity is equivalent to acceleration. the speed of light being constant. free fall. energy.
acceleration.
According to the principle of equivalence, gravity is equivalent to free fall. acceleration. speed of light being constant. energy.
does not have a precise position or a precise velocity.
According to the uncertainty principle, a particle such as an electron does not have a precise position or a precise velocity. has a precise position and a precise velocity, but the observer is unable to determine them. must have speeds smaller than the speed of light. can only occupy precise energy levels around the nucleus of an atom.
does not have a precise position or a precise velocity.
According to the uncertainty principle, a particle such as an electron must have speeds smaller than the speed of light. has a precise position and a precise velocity, but the observer is unable to determine them. can only occupy precise energy levels around the nucleus of an atom. does not have a precise position or a precise velocity.
galaxies farther away are moving away from us faster.
Astronomers know that the universe is expanding because most galaxies are moving away from us. galaxies farther away are moving away from us faster. everything is moving away from us. there is a cosmic microwave background.
moving away from them, the more distant galaxies moving faster.
Because of the general expansion of space, all distant galaxies appear to be moving away from us, with speeds that increase with distance from our Galaxy. Observers in one of these distant galaxies would apparently see all galaxies on one side of the observers moving toward them and all galaxies on the other side moving away from them; the more distant the galaxy, the faster its motion. moving away from them, with closer galaxies moving faster. moving away from them, the more distant galaxies moving faster. moving toward them, with more distant galaxies moving faster.
Figure A shows that the galaxies in the Universe are moving farther apart form each other because space between them is expanding. This is the correct description of our Universe.
Each dot represents a galaxy and time progresses from left to right. Which of these statements regarding Figures A and B is true? Figure A shows that the galaxies in the Universe are moving farther apart form each other because space between them is expanding. This is the correct description of our Universe. Figure B shows that the Big Bang occurred somewhere in existing space and galaxies are moving apart from each other within this space because of the explosion. This is the correct description of our Universe. Figure B shows that the galaxies in the Universe are moving farther apart form each other because space between them is expanding. This is the correct description of our Universe. Figure A and Figure B are both valid descriptions of our Universe because galaxies are moving farther away from each other in both scenarios.
that all electromagnetic radiation approaches an observer at the speed of light, regardless of the motion of the observer or emitter.
Einstein's Special Theory of Relativity, put forth in 1905, is based on the idea that all electromagnetic radiation approaches an observer at the speed of light, regardless of the motion of the observer or emitter. that the trajectories of objects in space are determined by the curvature of spacetime. of quantum mechanics, which indicates that predicting certain events (especially at the particle level) is a science of probabilities. that the Universe originated in a Big Bang.
distant galaxies only
For which objects in the universe has the Hubble relation been shown to hold experimentally?
William Herschel
He assembled one of the first maps of the Milky Way in 1785 (shown in the picture below), which led him to the correct conclusion that it is shaped like a disk. Edwin Hubble Harlow Shapley William Herschel Albert Einstein
James Clerk Maxwell
He showed that light is an electromagnetic wave. Neils Bohr Max Planck James Clerk Maxwell Albert Einstein
Louis de Broglie
He was the first person to suggest that particles have wave-like properties. Werner Heisenberg Edwin Schrodinger Louis de Broglie Albert Einstein
He converted shifts in the wavelengths of lines in the galaxy spectra to velocities using the Doppler effect.
How did Edwin Hubble measure the velocities of distant galaxies to build his famous diagram? He extrapolated from the rotation velocities of nearby galaxies. He measured the periods of Cepheid variables and converted them to velocities. He converted shifts in the wavelengths of lines in the galaxy spectra to velocities using the Doppler effect. He converted shifts in the luminosities of the galaxies to velocities using gravitational lensing.
bend towards the star due to gravity.
If light from a distant star passes close to a massive body, the light beam will
accelerated observers would find that light beams bend, so gravity must also bend light beams.
In coming to the conclusion that light beams are bent by gravity, Einstein reasoned that since all observers experience the same laws of physics, Newton's theory of gravity must apply to light beams. since light speed is the same for all observers, moving observers would observe that light beams bend. fast-moving observers would find that light beams bend, so gravity must also bend light beams. accelerated observers would find that light beams bend, so gravity must also bend light beams.
newly created galaxies fill in the space between existing galaxies as the Universe expands.
In the Steady State model of the Universe galaxies steadily move apart with increasing velocity as the Universe expands. dark energy is causing galaxies to move faster away from each other. newly created galaxies fill in the space between existing galaxies as the Universe expands. the Universe is infinite and has an unchanging number of galaxies.
distant supernovae
Observations of these revealed that the expansion of the Universe is accelerating. Cepheid variable stars cosmic microwave background photons distant galaxies distant supernovae
is accelerating (speeding up).
Recent results from very bright supernovae in very distant galaxies seem to indicate that the expansion of the universe has now stopped and the universe will shortly begin to contract again toward a recollapse. is accelerating (speeding up). is continuing at a constant rate and has done so since just after the Big Bang. is decelerating (slowing down).
All statements are true.
The "Milky Way" refers to the glowing band of light that can be seen to extend across the night sky. All statements are true. is one of many spiral galaxies in the Universe. contains many stars and gaseous nebulae including dark nebulae, reflection nebulae, and emission nebulae.
inverse time (1/s)
The Hubble constant has units of km/s inverse time (1/s) time (s) Mpc
a list of some of the brightest star clusters, neublae, and galaxies that are often looked at by amateur astronomers in the northern hemisphere with their small telescopes.
The Messier Catalog is a list of the 110 best asteroids and comets that are easily observed from the northern hemisphere. the catalog that gives the times when it is most favorable to observe the inner and outer planets. the catalog that gives tidal tables which is necessary when high and low tides need to be predicted exactly. a list of some of the brightest star clusters, neublae, and galaxies that are often looked at by amateur astronomers in the northern hemisphere with their small telescopes.
100 billion stars.
The Milky Way contains about 10 million stars. 100,000 stars. 100 million stars. 100 billion stars.
the General Theory of Relativity
The Solar eclipse of 1919 was used as a test for the presence of dark matter measuring the diameter of the Sun the luminosity of the Sun the General Theory of Relativity
the proton-proton chain.
The Sun generates energy through a process that combines 4 hydrogen nuclei to form a helium nucleus. The mass of the resulting helium nucleus is less than the combined masses of the 4 hydrogen nuclei. The excess mass is converted to energy as in the equation E = mc2. This process is called the proton-proton chain. gravitational contraction a hydrogen bomb the strong nuclear force
does not exist anywhere in space.
The center of the Universe does not exist anywhere in space. is where the Big Bang happened. is the Milky Way Galaxy since all galaxies are moving away from us. exists beyond our observable horizon.
the acceleration of the universe
The concept of dark energy has been introduced to explain which of the following? the darkness of the universe the expansion of the universe the unseen mass in the universe the acceleration of the universe
in the microwave band.
The leftover radiation from the Big Bang has a blackbody spectrum with a temperature of 3 degrees Kelvin. This spectrum peaks... in the infrared. in the microwave band. in the ultraviolet. in gamma-rays.
Star A is farther away from us than Star B.
The parallax of Star A is 0.1" and the parallax of Star B is 0.005". Which statement is true?
5 parsecs
The parallax of a star is measured to be 0.2 arcseconds. How far away is it?
the particle nature of light.
The photoelectric effect is explained by the wave nature of light. the particle nature of light. electrons being converted into photons. photons being converted into electrons.
is quite flat, even beyond the visible disk of the galaxy.
The rotation curve of a galaxy is a graph showing the galaxy's speed of rotation at different distances from the center. The observed rotation curve in the outer parts of a typical large spiral galaxy increases drastically with increasing distance from the center, as shown by the spiral arms. is quite flat, even beyond the visible disk of the galaxy. decreases suddenly to zero at the outer edge of the visible galaxy decreases smoothly with increasing distance from the center.
William Herschel
This person was the first to model the Milky Way as a disk of stars that was five times wider than its thickness and with the Sun at its center.
Planetary nebula
This type of astronomical object is formed when a Sun-like star ejects its outer layers, as its core shrinks to become a white dwarf. Planetary nebula Cepheid variable Asteroid Supernova
c and c, respectively
Velma is in a spaceship that travels past Mort at a speed of 0.25 c. She turns on a flashlight in the direction of motion of the spaceship. What speed does Mort measure for the speed of light from Velma's flashlight? If Velma turned the flashlight so that the light beam is pointing in the direction opposite to her direction of motion, what speed would Mort measure for the beam of light? c and 1.25 c, respectively c and c, respectively 1.25 c and 0.75 c, respectively c and 0.75 c, respectively
50 m/s in the direction of motion of the train
Velma is in a train that is moving at 70 m/s. She throws a baseball horizontally at 20 m/s in the opposite direction as the train. What speed does Mort, who is stationary with respect to the tracks, measure for the speed of the ball? 50 m/s in the direction of motion of the train 50 m/s in the direction opposite to the motion of the train 90 m/s in the direction opposite to the motion of the train 90 m/s in the direction of motion of the train
An Earth-based observer will see the beam approaching at 1.00c.
Velma's spaceship approaches Earth at 0.68c. She turns on a laser and beams it toward Earth. How fast does an Earth-based observer see the beam approaching Earth? An Earth-based observer will see the beam approaching at 1.68c. An Earth-based observer will see the beam approaching at 1.00c. An Earth-based observer will see the beam approaching at 0.32c. An Earth-based observer will see the beam approaching at 0.68c.
an interference pattern shows up on the screen when the experiment is run for a long enough time.
We know that electrons have wave-like properties because, in the double slit experiment with electrons, the screen is washed out and no pattern appears. the electrons create individual impact points on the screen that are randomly placed. two impact regions are visible, one for each slit. an interference pattern shows up on the screen when the experiment is run for a long enough time.
an unknown form of energy called dark energy
What do astronomers believe is causing the accelerated expansion of the Universe? dark matter that has properties of anti-gravity an unknown form of energy called dark energy pressure from photons in the cosmic microwave background weakly interacting massive particles or WIMPS
Gravity is the result of curved spacetime.
What explanation does general relativity provide for gravity?
a supermassive black hole in the center of a distant galaxy, where matter forms a rapidly rotating accretion disk as it falls in towards the black hole, emitting tremendous amounts of energy
What is a quasar? a supermassive black hole in the center of a distant galaxy, where matter forms a rapidly rotating accretion disk as it falls in towards the black hole, emitting tremendous amounts of energy an image created due to high gravity that has focused radiation from many sources by gravitational lensing, and thus it appears to be very bright a galaxy undergoing a steady series of supernova explosions a very rapidly rotating neutron star which creates jets, converts 10% of its mass to energy and causes tremendous heat and energy output
a supermassive black hole in the center of a distant galaxy, where matter forms a rapidly rotating accretion disk as it falls in towards the black hole, emitting tremendous amounts of energy
What is a quasar? a very rapidly rotating neutron star which creates jets, converts 10% of its mass to energy and causes tremendous heat and energy output a galaxy undergoing a steady series of supernova explosions a supermassive black hole in the center of a distant galaxy, where matter forms a rapidly rotating accretion disk as it falls in towards the black hole, emitting tremendous amounts of energy an image created due to high gravity that has focused radiation from many sources by gravitational lensing, and thus it appears to be very bright
Their brightness varies periodically and the longer the period of brightness variation, the more intrinsically luminous they are.
What is special about Cepheid variable stars?
the stretching of the wavelengths of photons as they travel through expanding space
What is the "cosmological redshift"? the increasing wavelengths of photons by the Doppler shift, because they are emitted by galaxies that are moving away from us the loss of energy of photons as they interact with particles in the universe, so that their wavelengths gradually increase as they travel toward us through space the stretching of the wavelengths of photons as they travel through expanding space the stretching of the wavelengths of photons as they pass through absorbing matter in galaxies between us and the emitting galaxy
100,000 lys
What is the size of the Milky Way Galaxy?
It is at least 100 kpc across.
What is the size of the dark matter halo of the Milky Way galaxy? It is about the size of the halo of globular clusters, which is about 30 kpc across. It is the size of the central black hole, which is about 40 light seconds across. It is at least 100 kpc across. It is the size of the galactic bulge.
70 km/s/Mpc
What is the value of the Hubble constant?
Betelgeuse is a cool star and Rigel is a hot star.
What makes Betelgeuse look distinctly red and Rigel distinctly blue? Betelgeuse is a hot star and Rigel is a cool star. Betelgeuse is an emission line nebula and Rigel is a reflection nebula. Betelgeuse is covered by a dusty nebula and emits mostly in the infrared while Rigel is not covered by dust, thereby letting its ultraviolet light shine through. Betelgeuse is a cool star and Rigel is a hot star.
The spectral lines were shifted towards the red by amounts that were previously not seen.
What was odd about the discovery spectrum of the first identified quasar? The positions of the spectral lines showed that the quasar was approaching us with speeds close to the speed of light. The spectral lines did not correspond to any known element. The spectral lines were shifted towards the red by amounts that were previously not seen. The spectral lines were too blurry to be identified correctly.
white dwarf
What will the Sun become at the end of its life? white dwarf black hole neutron star red giant
all directions equally
Where does the cosmic microwave background radiation come from? the center of the Universe the radio antenna at Bell labs all directions equally the edge of the Universe
some of them are radio stars and not galaxies
Which of the following is NOT a characteristic of an active galaxy? luminosities higher than can be explained by the light from stars alone broad emission lines indicative of rapid internal rotation jets that can extend much farther than their optical extent some of them are radio stars and not galaxies
Measure the time it takes light to get from the source to Earth.
Which of the following is not a valid technique to measure distances in astronomy? Measure the period of a Cepheid variable and its apparent brightness, and calculate the distance using the period-luminosity relation of Cepheids and the inverse square law. Measure the time it takes light to get from the source to Earth. Measure the parallactic angle of a star and calculate the distance using parallax. Measure the recession velocity of a galaxy from the redshift of its spectrum, and calulate the distance using the known value of the Hubble constant, H0.
Barred spiral
Which of the following type of galaxy is most similar to the Milky Way? Elliptical Barred spiral Spiral Irregular
supermassive black holes in the centers of galaxies
Which of these is not an indicator of the presence of dark matter? arcs (distorted images of background galaxies) around massive clusters of galaxies supermassive black holes in the centers of galaxies the high velocities of galaxies in clusters fast rotation speeds at the edges of spiral galaxies
supermassive black holes in the centers of galaxies
Which of these is not an indicator of the presence of dark matter? the high velocities of galaxies in clusters supermassive black holes in the centers of galaxies fast rotation speeds at the edges of spiral galaxies arcs (distorted images of background galaxies) around massive clusters of galaxies
Sirius
Which of these is the brightest star in the night sky?
the detection of many black hole candidates in the Milky Way Galaxy
Which of these observations is not a confirmation of the Theory of General Relativity? the detection of many black hole candidates in the Milky Way Galaxy images showing arcs of distant galaxies around foreground galaxy clusters the precession of the orbit of Mercury the shift in positions of stars during a solar eclipse
The CMB was created when the Universe was 100,000,000 years old at a time when the first stars formed. Microwave radiation has been streaming through space ever since.
Which of these statements about when and how the cosmic microwave background radiation was created is FALSE? When the CMB was created, electrons were able to combine with protons to form hydrogen atoms. The photons were no longer trapped in the plasma; they began to stream through space and we observe them today in the form of microwave radiation. At the time the CMB was created, the Universe was a hot plasma at a temperature of about 3,000 degrees Celsius. The CMB was created when the Universe was 100,000,000 years old at a time when the first stars formed. Microwave radiation has been streaming through space ever since. The CMB was created when the Universe was 380,000 year old.
Planck showed that radiation had to be quantized (i.e., it came in discrete packets of energy) and Einstein used this idea to explain the photoelectric effect
Which of these statements is true? The Bohr model of the atom is one in which the electron exists in a cloud, and the electron can have a range of possible energies within each state. Louis de Broglie explained that the Sun produced its energy through fusion reactions where hydrogen is converted to helium via the proton-proton chain. Planck showed that radiation had to be quantized (i.e., it came in discrete packets of energy) and Einstein used this idea to explain the photoelectric effect The Schrodinger uncertainty principle implies that we can never be sure whether the cat in the proverbial box is dead or not because it exists in a superposition (combination) of both possibilities.
the distance to the object and the redshift of its light
Which two parameters representing observations of distant objects in the universe are related in the Hubble Law?
when helium was formed, the expansion cooled the Universe below 100 million K, which is the temperature required for helium to fuse into heavier elements.
Why didn't nuclei heavier than helium form in the Big Bang? when helium was formed, the expansion cooled the Universe below 100 million K, which is the temperature required for helium to fuse into heavier elements. There was not enough matter in the Universe at that time. Only supernovae can produce heavier nuclei. The electrons slowed down enough to be captured into orbits by protons.
Because the mass of the resulting helium nucleus is smaller than the mass of the four hydrogen nuclei required to form it.
Why does the fusion of hydrogen into helium release energy? Because fusion breaks the electromagnetic bonds between hydrogen atoms, releasing energy. Because the mass of the resulting helium nucleus is larger than the mass of the four hydrogen nuclei required to form it. Because the mass of the resulting helium nucleus is smaller than the mass of the four hydrogen nuclei required to form it. Because the velocity of four hydrogen nuclei is larger than the velocity of a helium nucleus.