Final Exam Flashcards
(132 cards)
1
Q
Two stars have the same luminosity. Star X is spectral type F, while Star Y is spectral type K. Therefore, Star X is larger in radius than Star Y.
True or False.
A
False.
2
Q
Who is the astronomer indicated by the “H” in the H-R diagram?
a) Hubble
b) Henry
c) Hertzsprung
d) Huggins
e) Hoyle
A
c) Hertzsprung
3
Q
A star has spectral lines of molecules in its atmosphere. Which of the spectral types listed below is it most likely to belong to?
a) A
b) B
c) G
d) M
e) O
A
d) M
4
Q
Which type of star has the strongest Balmer lines of hydrogen?
a) A
b) B
c) G
d) M
e) O
A
a) A
5
Q
This person reorganized the spectral classification scheme into the one we use today and personally classified over 400,000 stars.
a) Annie Jump Cannon
b) Williamina Fleming
c) Cecilia Payne-Gaposchkin
d) Henry Draper
e) Edward Pickering
A
a) Annie Jump Cannon
6
Q
Which of the following statements about apparent and absolute magnitudes is true?
a) The magnitude system that we use now is based on a system used by the ancient Greeks over 2,000 years ago that classified stars by how bright they appeared.
b) A star with apparent magnitude 1 is brighter than one with apparent magnitude 2.
c) The absolute magnitude of a star is another measure of its luminosity.
d) A star’s absolute magnitude is the apparent magnitude it would have if it were at a distance of 10 parsecs from Earth.
e) All of the above are true.
A
e) All of the above are true.
7
Q
The faintest star visible to the naked eye has an apparent visual magnitude of about:
a) 10
b) 6
c) 1
d) 0
e) -6
A
b) 6
8
Q
On a Hertzsprung-Russell diagram, where on the main sequence would we find stars that have the greatest mass?
a) Upper right
b) Lower right
c) Upper left
d) Lower left
e) There are no trends in mass on the main sequence
A
c) Upper left
9
Q
The spectral sequence in order of decreasing temperature is:
a) OFBAGKM
b) OBAGFKM
c) OBAFGKM
d) ABFGKMO
e) BAGFKMO
A
c) OBAFGKM
10
Q
A planet is detected via the Doppler technique. The repeating pattern of the star’s radial velocity curve tells us:
a) The planet’s size
b) The planet’s mass
c) The planet’s density
d) The orbital period of the planet
e) The orbital eccentricity of the planet
A
d) The orbital period of the planet
11
Q
Cluster ages can be determined from:
a) main sequence fitting
b) main sequence turnoff
c) pulsating variable stars
d) spectroscopic binaries
e) visual binaries
A
b) main sequence turnoff
12
Q
Hydrogen fusion in the Sun requires a temperature (in Kelvin) of:
a) thousands of degrees
b) millions of degrees
c) billions of degrees
d) trillions of degrees
e) any temperature, as long as gravity is strong enough
A
b) millions of degrees
13
Q
In the late 1800s, Kelvin and Helmholtz suggested that the Sun stayed hot thanks to gravitational contraction. What was the major drawback of this idea?
a) it predicted that the Sun could last only about 25 million years, which is far less than the age of Earth
b) it predicted that the Sun would shrink noticeably as we watched it, and the Sun appears to be stable in size
c) it is physically impossible to generate heat simply by making a star shrink in size
d) it predicted that Earth would also shrink, which would make it impossible to have stable geology on our planet
e) it was proposed before Einstein’s theory of general relativity and was therefore incorrect
A
a) it predicted that the Sun could last only about 25 million years, which is far less than the age of Earth
14
Q
What two forces are balanced in what we call gravitational equilibrium?
a) the electromagnetic force and gravity
b) outward pressure and the strong force
c) outward pressure and gravity
d) the strong force and gravity
e) the strong force and kinetic energy
A
c) outward pressure and gravity
15
Q
When is/was gravitational contraction an important energy-generation mechanism for the Sun?
a) only during solar minimum
b) only during solar maximum
c) when the Sun was being formed from a collapsing cloud of gas
d) right after the Sun began fusing hydrogen in its core
e) when the Sun transports radiation through the convection zone
A
c) when the Sun was being formed from a collapsing cloud of gas
16
Q
What do we mean when we say that the Sun is in gravitational equilibrium?
a) the hydrogen gas in the Sun is balanced so that it never rises upward or falls downward
b) the Sun maintains a steady temperature
c) this is another way of stating that the Sun generates energy by nuclear fusion
d) there is a balance within the Sun between the outward push of pressure and the inward pull of gravity
e) the Sun always has the same amount of mass, creating the same gravitational force
A
d) there is a balance within the Sun between the outward push of pressure and the inward pull of gravity
17
Q
How does the Sun generate energy today?
a) nuclear fission
b) nuclear fusion
c) chemical reactions
d) gravitational contraction
e) gradually expanding in size
A
b) nuclear fusion
18
Q
At approximately what temperature can helium fusion occur?
a) 100,000 K
b) 1 million K
c) a few million K
d) 100 million K
e) 100 billion K
A
d) 100 million K
19
Q
White dwarfs are so called because:
a) they are both very hot and very small
b) they are the end-products of small, low-mass stars
c) they are the opposite of black holes
d) it amplifies the contrast with red giants
e) they are supported by electron degeneracy pressure
A
a) they are both very hot and very small
20
Q
A teaspoonful of white dwarf material on Earth would weigh:
a) the same as a teaspoonful of Earth-like material
b) about the same as Mt. Everest
c) about the same as Earth
d) a few tons
e) a few million tons
A
d) a few tons
21
Q
Which of the following is closest in mass to a white dwarf?
a) the Moon
b) Earth
c) Jupiter
d) Neptune
e) the Sun
A
e) the Sun
22
Q
If you were to come back to our Solar System in 6 billion years, what might you expect to find?
a) a red giant star
b) a white dwarf
c) a rapidly spinning pulsar
d) a black hole
e) Everything will be pretty much the same as it is now
A
b) a white dwarf
23
Q
Why are Cepheid variables important?
a) Cepheid variables are stars that vary in brightness because they harbor a black hole
b) Cepheids are pulsating variable stars, and their pulsation periods are directly related to their true luminosities. Hence, we can use Cepheids as “standard candles” for distance measurements
c) Cepheids are a type of young galaxy that helps us understand how galaxies form
d) Cepheids are supermassive stars that are on the verge of becoming supernovae and therefore allow us to choose candidates to watch if we hope to observe a supernova in the near future
A
b) Cepheids are pulsating variable stars, and their pulsation periods are directly related to their true luminosities. Hence, we can use Cepheids as “standard candles” for distance measurements
24
Q
What is a standard candle?
a) an object for which we are likely to know the true luminosity
b) an object for which we can easily measure the apparent brightness
c) a class of objects in astronomy that all have exactly the same luminosity
d) any star for which we know the exact apparent brightness
e) a long, tapered candle that lights easily
A
a) an object for which we are likely to know the true luminosity
25
Since all stars begin their lives with the same basic composition, what characteristic most determines how they will differ?
a) location where they are formed
b) time they are formed
c) luminosity they are formed with
d) mass they are formed with
e) color they are formed with
d) mass they are formed with
26
Which of the following sequences correctly describes the stages of life for a low-mass star?
a) red giant, protostar, main-sequence, white dwarf
b) white dwarf, main-sequence, red giant, protostar
c) protostar, red giant, main-sequence, white dwarf
d) protostar, main-sequence, white dwarf, red giant
e) protostar, main-sequence, red giant, white dwarf
e) protostar, main-sequence, red giant, white dwarf
27
If the Boltzmann equation indicates that O and B class stars should have stronger Balmer lines, why do we see these lines strongest in A class stars and get weaker in O and B class stars?
More H atoms are in the n=2 state in A stars than O or B stars. H is more abundant in A stars than O or B stars.
28
The most common form of iron has 26 protons and 30 neutrons. What is the atomic number, atomic mass number, and number of electrons (assuming the atom is neutral) for this form of iron?
atomic number = 26
atomic mass number = 56
number of electrons = 26
29
Consider the following three atoms: atom 1 has 7 protons and 8 neutrons; atom 2 has 8 protons and 7 neutrons; atom 3 has 8 protons and 8 neutrons. Which two atoms are isotopes of the same element?
Atoms 2 and 3 are isotopes.
30
Oxygen has atomic number 8. How many times must an oxygen atom be ionized to create an O+5 ion? How many electrons are in an O+5 ion? Write this ion using spectroscopic notation.
O+5 is 5x ionized
3e-
OVI
31
Why is there an upper limit to the mass of a white dwarf?
a) White dwarfs form only from stars smaller than 1.4 solar masses.
b) The more massive the white dwarf, the greater the degeneracy pressure and the faster the speeds of its electrons. Near 1.4 solar masses, the speeds of the electrons approach the speed of light, so more mass cannot be added without breaking the degeneracy pressure.
c) The more massive the white dwarf, the higher its temperature and hence the greater its degeneracy pressure. At about 1.4 solar masses, the temperature becomes so high that all matter effectively melts, even individual subatomic particles.
d) The upper limit to the masses of white dwarfs was determined through observations of white dwarfs, but no one knows why the limit exists.
e) Above this mass, the electrons would be pushed together so closely they would turn into neutrons and the star would become a neutron star.
b) The more massive the white dwarf, the greater the degeneracy pressure and the faster the speeds of its electrons. Near 1.4 solar masses, the speeds of the electrons approach the speed of light, so more mass cannot be added without breaking the degeneracy pressure.
32
The Schwarzschild radius of a body is:
a) the distance from its center at which nuclear fusion ceases.
b) the distance from its surface at which an orbiting companion will be broken apart.
c) the maximum radius a white dwarf can have before it collapses.
d) the maximum radius a neutron star can have before it collapses.
e) the radius of a body at which its escape velocity equals the speed of light.
e) the radius of a body at which its escape velocity equals the speed of light.
33
Which kinds of stars are most common in a newly formed star cluster?
a) O stars
b) G stars
c) M stars
c) M stars
34
The typical size of interstellar dust particles is ______; and they consist mainly of _______.
a) 1 cm; silicates and carbon compounds
b) 1 mm; hydrogen and helium
c) about a micrometer or less; silicates and carbon compounds
d) about a nanometer or less; hydrogen and helium
c) about a micrometer or less; silicates and carbon compounds
35
By mass, the interstellar medium in our region of the Milky Way consists of:
a) 70% Hydrogen, 30% Helium.
b) 70% Hydrogen, 28% Helium, 2% heavier elements.
c) 70% Hydrogen, 20% Helium, 10% heavier elements.
d) 50% Hydrogen, 50% Helium.
e) 50% Hydrogen, 30% Helium, 20% heavier elements.
b) 70% Hydrogen, 28% Helium, 2% heavier elements.
36
The most abundant molecule in molecular clouds is:
a) H2
b) He2
c) CO
d) H2O
e) HHe
a) H2
37
What is the range of timescales for star formation?
a) from 1 million years for the most massive stars up to 10 million years for the least massive stars
b) from 1 million years for the most massive stars up to 100 million years for the least massive stars
c) from 1 million years for the least massive stars up to 10 million years for the most massive stars
d) from 1 million years for the least massive stars up to 100 million years for the most massive stars
e) about 30 million years for all stars, whatever mass
b) from 1 million years for the most massive stars up to 100 million years for the least massive stars
38
What is the smallest mass a newborn star can have?
a) 8 times the mass of Jupiter
b) 80 times the mass of Jupiter
c) 800 times the mass of Jupiter
d) about 1/80 the mass of our Sun
e) about 1/800 the mass of our Sun
b) 80 times the mass of Jupiter
39
What are the letters that follow the spectral sequence OBAFGKM?
a) NP
b) YZ
c) LT
d) CD
e) UV
c) LT
40
What is the greatest mass a newborn star can have:
a) 10 solar masses.
b) 20 solar masses.
c) 50 solar masses.
d) 150 solar masses.
e) 300 solar masses.
d) 150 solar masses.
41
Which element has the lowest mass per nuclear particle and therefore cannot release energy by either fusion or fission?
a) hydrogen
b) oxygen
c) silicon
d) iron
e) uranium
d) iron
42
What happens when the gravity of a massive star is able to overcome neutron degeneracy pressure?
a) The core contracts and becomes a white dwarf.
b) The core contracts and becomes a ball of neutrons.
c) The core contracts and becomes a black hole.
d) The star explodes violently, leaving nothing behind.
e) Gravity is not able to overcome neutron degeneracy pressure.
c) The core contracts and becomes a black hole.
43
Which event marks the beginning of a supernova?
a) the onset of helium burning after a helium flash in a star with mass comparable to that of the Sun
b) the sudden outpouring of X rays from a newly formed accretion disk
c) the sudden collapse of an iron core into a compact ball of neutrons
d) the beginning of neon burning in an extremely massive star
e) the expansion of a low-mass star into a red giant
c) the sudden collapse of an iron core into a compact ball of neutrons
44
Degeneracy pressure is the source of the pressure that stops the crush of gravity in all the following except:
a) a brown dwarf.
b) a white dwarf.
c) a neutron star.
d) a very massive main-sequence star.
e) the central core of the Sun after hydrogen fusion ceases but before helium fusion begins.
d) a very massive main-sequence star.
45
What causes the radio pulses of a pulsar?
a) The star vibrates.
b) As the star spins, beams of radio radiation sweep through space. If one of the beams crosses Earth, we observe a pulse.
c) The star undergoes periodic explosions of nuclear fusion that generate radio emission.
d) The star's orbiting companion periodically eclipses the radio waves emitted by the main pulsar.
e) A black hole near the star absorbs energy and re-emits it as radio waves.
b) As the star spins, beams of radio radiation sweep through space. If one of the beams crosses Earth, we observe a pulse.
46
How does a black hole form from a massive star?
a) During a supernova, if a star is massive enough for its gravity to overcome neutron degeneracy of the core, the core will be compressed until it becomes a black hole.
b) Any star that is more massive than 8 solar masses will undergo a supernova explosion and leave behind a black-hole remnant.
c) If enough mass is accreted by a white-dwarf star so that it exceeds the 1.4-solar-mass limit, it will undergo a supernova explosion and leave behind a black-hole remnant.
d) If enough mass is accreted by a neutron star, it will undergo a supernova explosion and leave behind a black-hole remnant.
e) A black hole forms when two massive main-sequence stars collide.
a) During a supernova, if a star is massive enough for its gravity to overcome neutron degeneracy of the core, the core will be compressed until it becomes a black hole.
47
Observationally, how can we tell the difference between a white-dwarf supernova and a massive- star supernova?
a) A massive-star supernova is brighter than a white-dwarf supernova.
b) A massive-star supernova happens only once, while a white-dwarf supernova can repeat periodically.
c) The spectrum of a massive-star supernova shows prominent hydrogen lines, while the spectrum of a white-dwarf supernova does not.
d) The light of a white-dwarf supernova fades steadily, while the light of a massive-star supernova brightens for many weeks.
e) We cannot yet tell the difference between a massive-star supernova and a white-dwarf supernova.
c) The spectrum of a massive-star supernova shows prominent hydrogen lines, while the spectrum of a white-dwarf supernova does not.
48
After a massive-star supernova, what is left behind?
a) Always a white dwarf.
b) Always a neutron star.
c) Always a black hole.
d) Either a white dwarf or a neutron star.
e) Either a neutron star or a black hole.
e) Either a neutron star or a black hole.
49
What is the basic definition of a black hole?
a) Any compact mass that emits no light.
b) A dead star that has faded from view.
c) Any object from which the escape velocity exceeds the speed of light.
d) Any object made from dark matter.
e) A dead galactic nucleus that can only be viewed in infrared.
c) Any object from which the escape velocity exceeds the speed of light.
50
What is the ultimate fate of an isolated white dwarf?
a) It will cool down and become a cold black dwarf.
b) As gravity overwhelms the electron degeneracy pressure, it will explode as a nova.
c) As gravity overwhelms the electron degeneracy pressure, it will explode as a supernova.
d) As gravity overwhelms the electron degeneracy pressure, it will become a neutron star.
e) The electron degeneracy pressure will eventually overwhelm gravity and the white dwarf will slowly evaporate.
a) It will cool down and become a cold black dwarf.
51
When does a protostar become a true star?
a) When the star is 1 million years old.
b) When the central temperature reaches 1 million Kelvin.
c) When nuclear fusion begins in the core.
d) When the thermal energy becomes trapped in the center.
e) When the stellar winds and jets blow away the surrounding material.
c) When nuclear fusion begins in the core.
51
What is interstellar reddening?
a) Interstellar dust absorbs more red light than blue light, making stars appear redder than their true color.
b) Interstellar dust absorbs more red light than blue light, making stars appear bluer than their true color.
c) Interstellar dust absorbs more blue light than red light, making stars appear redder than their true color.
d) Interstellar dust absorbs more blue light than red light, making stars appear bluer than their true color.
e) The spectral line shift due to a star's motion through the interstellar medium.
c) Interstellar dust absorbs more blue light than red light, making stars appear redder than their true color.
51
If you wanted to observe stars behind a molecular cloud, in what wavelength of light would you most likely observe?
a) Ultraviolet.
b) Visible.
c) Infrared.
d) X-ray.
e) Gamma-ray.
c) Infrared.
52
What is the ultimate fate of an isolated pulsar?
a) It will spin ever faster, becoming a millisecond pulsar.
b) As gravity overwhelms the neutron degeneracy pressure, it will explode as a supernova.
c) As gravity overwhelms the neutron degeneracy pressure, it will become a white dwarf.
d) It will slow down, the magnetic field will weaken, and it will become invisible.
e) The neutron degeneracy pressure will eventually overwhelm gravity and the pulsar will slowly evaporate.
d) It will slow down, the magnetic field will weaken, and it will become invisible.
53
Levels of the Sun's composition:
Core
Radiation Zone
Convection Zone
Photosphere
Chromosphere
Corona
Solar Wind
54
The Sun is located in the _______ of the Milky Way.
a) Nuclear bulge
b) Center
c) Spheroid
d) Halo
e) Disk
e) Disk
55
The greater number of heavy elements seen in the spectra of Population I stars relative to Population II stars is explained by the fact that Population I stars:
a) have planetary systems and debris from these fall onto the stars surface.
b) are older and have therefore fused more hydrogen into heavy elements.
c) formed more recently and have therefore been made from enriched stellar gas.
d) are colder than therefore exhibit strong “metal” lines.
c) formed more recently and have therefore been made from enriched stellar gas.
56
What produces the 21-cm line that we use to map out the Milky Way Galaxy?
a) atomic hydrogen
b) ionized hydrogen
c) molecular hydrogen
d) carbon monoxide
e) helium
a) atomic hydrogen
57
Where do dust grains form?
a) in supernovae
b) in the winds of red giant stars
c) in planetary nebulae
d) in molecular clouds
e) all of the above
e) all of the above
58
Which of the following statements about globular clusters is false?
a) Globular clusters contain many thousands of stars.
b) Globular cluster stars are more than 12 billion years old.
c) Globular cluster ages increase with distance from the Milky Way.
d) Globular clusters are distributed spherically around the Milky Way.
e) Globular cluster stars are very metal-poor relative to the Sun.
c) Globular cluster ages increase with distance from the Milky Way.
59
What two quantities did Edwin Hubble plot against each other to discover the expansion of the Universe?
a) velocity and distance
b) luminosity and distance
c) velocity and temperature
d) luminosity and temperature
e) age and distance
a) velocity and distance
60
What is interstellar reddening?
a) Interstellar dust absorbs more red light than blue light, making stars appear redder than their true color.
b) Interstellar dust absorbs more red light than blue light, making stars appear bluer than their true color.
c) Interstellar dust absorbs more blue light than red light, making stars appear redder than their true color.
d) Interstellar dust absorbs more blue light than red light, making stars appear bluer than their true color.
e) The spectral line shift due to a star's motion through the interstellar medium.
c) Interstellar dust absorbs more blue light than red light, making stars appear redder than their true color.
61
What is the greatest mass a newborn star can have:
a) 10 solar masses.
b) 20 solar masses.
c) 50 solar masses.
d) 150 solar masses.
e) 300 solar masses.
d) 150 solar masses.
62
__________ is not one of the following types of galaxies found in the Hubble sequence?
a) Barred Elliptical
b) Elliptical
c) Barred Spiral
d) Spiral
e) Irregular
a) Barred Elliptical
63
Spectroscopic observations of the star Vega show that its hydrogen lines are blue shifted with respect to the rest wavelength. Based on these observations we can conclude that Vega is _______.
a) Moving toward us
b) Moving away from us
c) Is at rest with respect to us
d) There is no way to tell Vega’s motion from this data
a) Moving toward us
64
If you wanted to observe stars behind a molecular cloud, in what wavelength of light would you most likely observe?
a) ultraviolet
b) visible
c) infrared
d) X-ray
e) gamma-ray
c) infrared
65
Elliptical galaxies typically contain lots of gas and dust and are sites of active star formation.
a) True
b) False
b) False
66
Astronomers think the Milky Way has spiral arms because:
a) they can see them unwinding along the celestial equator.
b) radio maps show that gas clouds are distributed in the disk with a spiral pattern.
c) young star clusters, HII regions, and associations outline spiral arms.
d) globular clusters outline spiral arms.
e) both (b) and (c) are correct.
e) both (b) and (c) are correct.
67
The length of time a star spends fusing hydrogen into helium is called its main sequence lifetime.
a) True
b) False
a) True
68
A brown dwarf is:
a) A failed star; its mass is too small for nuclear fusion to ever occur
b) An early stage of star formation, when pressure halts the collapse of a star, before nuclear fusion begins
c) The end stage of a low mass star, like the Sun
d) The end stage of a high mass star, like Betelgeuse
e) An extremely small, cool main sequence star
a) A failed star; its mass is too small for nuclear fusion to ever occur
69
A planetary nebula (e.g., the Ring nebula) is a region of planetary formation around a star.
a) True
b) False
b) False
70
The major stages in the life cycle of the Sun from birth to death (in order) are:
a) Interstellar cloud, red giant, main sequence star, protostar, planetary nebula and neutron star
b) Interstellar cloud, red giant, main sequence star, protostar, planetary nebula and white dwarf
c) Interstellar cloud, protostar, main sequence star, supergiant, supernova, and neutron star
d) Interstellar cloud, protostar, main sequence star, red giant, planetary nebula and white dwarf
d) Interstellar cloud, protostar, main sequence star, red giant, planetary nebula and white dwarf
71
What is the inner core of a massive supergiant star composed of when it reaches the end of its life (immediately before supernova explosion)?
a) Hydrogen (H)
b) Helium (He)
c) Carbon (C)
d) Silicon (Si)
e) Iron (Fe)
e) Iron (Fe)
72
This individual worked on classifying stellar spectra and created the spectral type sequence that is used to classify stars today.
a) Harlow Shapley
b) Henrietta Leavitt
c) Henry Norris Russel
d) Einar Hertzsprung
e) Annie Cannon
e) Annie Cannon
73
A pulsar is a(n):
a) Black hole
b) Rotating neutron star
c) Rotating white dwarf
d) Oscillating black hole
e) Oscillating protostar
b) Rotating neutron star
74
The spectral sequence (classes) in order from hottest to coolest is:
a) OABFGKM
b) OBAGFKM
c) MKGFBAO
d) OBAFGKM
e) MKFGABO
d) OBAFGKM
75
Aldebaran is a red star in Taurus. Vega is a blue star in Lyra. Which star is hotter (assuming no dust)?
a) Aldebaran
b) Vega
c) They are both the same temperature
d) It is impossible to tell
b) Vega
76
Star A is 5 times farther from the Earth than star B. Which star has a larger stellar parallax?
a) Star A
b) Star B
c) Stellar parallax for each one is the same.
b) Star B
77
Low mass stars (1 solar mass and below) are more common than high mass stars.
a) True
b) False
a) True
78
Rigel is much more luminous than Sirius. Rigel and Sirius have the same temperature. Which Star has the greater surface area (larger radius)?
a) Rigel
b) Sirius
c) Their surface areas are the same
d) Not enough information
a) Rigel
79
An ‘M’ main sequence star is more massive than an ‘A’ main sequence star.
a) True
b) False
b) False
80
Deneb has an apparent magnitude of +1.25. Vega has an apparent magnitude of +0.03. Arcturus has an apparent magnitude of –0.04. Which star appears brightest in our sky?
a) Deneb
b) Vega
c) Arcturus
d) They all appear the same brightness
e) Impossible to tell from the given information
c) Arcturus
81
White dwarf stars in binary star systems have the possibility of becoming Novae.
a) True
b) False
a) True
82
How would the apparent brightness of Alpha Centauri change if it were three times farther away?
a) It would only be 1/3 as bright
b) It would only be 1/6 as bright
c) It would only be 1/9 as bright
d) It would be 3 times brighter
c) It would only be 1/9 as bright
83
Population I stars are found primarily in the disks and spiral arms of galaxies.
a) True
b) False
a) True
84
You observe two stars with the same luminosity and determine that one is larger than the other. Which star has the greater temperature?
a) The smaller star
b) The larger star
c) The temperature is the same
a) The smaller star
85
Type Ia super nova events can be used to determine distances because their luminosities are well known (i.e., they are “standard candles”).
a) True
b) False
a) True
86
What causes the radio pulses of a pulsar?
a) The star vibrates
b) As the star spins, beams of radio radiation from it sweep through space; if one of these beams points toward the Earth, we observe a pulse
c) The star accretes matter from a companion, and undergoes periodic nuclear fusions that generate radio emission
d) This occurs in astrometric binary star systems, where the star’s dark orbiting companion periodically eclipses the radio waves emitted by the main star
e) A black hole near the star absorbs energy from it and remits the energy as radio pulses
b) As the star spins, beams of radio radiation from it sweep through space; if one of these beams points toward the Earth, we observe a pulse
87
Alpha Centauri is a G2V star. Capella is a G2III star. Alpha Centauri is on the main sequence, Capella is not.
a) True
b) False
a) True
88
A supernovae resulting from core collapse of a massive star (greater than 8 solar masses) is a _________ supernovae.
a) Type Ia
b) Type II
c) OB Type
d) Periodic
b) Type II
89
A photon is emitted from an atom when ________.
a) An electron is absorbed.
b) An electron jumps from a higher to a lower energy level
c) Atoms cannot emit photons
d) An electron jumps from a lower to a higher energy level
b) An electron jumps from a higher to a lower energy level
90
Betelgeuse: MV= -7.2 mV= 0.50; Deneb: MV= -7.2 mV= 1.25; which star is closer to the Sun?
a) Betelgeuse.
b) Deneb
c) They are the same distance
d) Impossible to tell from the given information.
a) Betelgeuse.
91
Compared to red light, blue light is:
a) More affected by interstellar extinction
b) Less affected by interstellar extinction
c) Affected the same by interstellar extinction
d) Unaffected by interstellar extinction
a) More affected by interstellar extinction
92
The Sloan Digital Sky Survey (SDSS) has measured distances to over one million galaxies.
a) True
b) False
a) True
93
Most stars have spectra showing dark lines against a continuous background of color. This observation indicates that these stars _________.
a) Are made almost entirely of hot, low-density gas.
b) Are made almost entirely of cool, low-density gas.
c) Have a warm interior that shines through a hotter, high-density gas.
d) Have a hot interior that shines through a cooler, low-density gas.
d) Have a hot interior that shines through a cooler, low-density gas.
94
Which of the following is not a major accomplishment of Edwin Hubble?
a) Devised a classification scheme for galaxies in 1925, which we still use today.
b) Discovered a law, which is now named after him, that describes the expansion of the universe.
c) Discovered the existence of Cepheid variables and their period-luminosity relationship.
d) Found Cepheid variables in Andromeda, and thus, determined the distance to Andromeda.
e) All of these are accomplishments of Edwin Hubble.
c) Discovered the existence of Cepheid variables and their period-luminosity relationship.
95
Distant galaxies have higher recessional velocities is a ____ statement about the expansion of the universe.
a) True
b) False
a) True
96
Quasars are:
a) Extremely luminous
b) Probably powered by super massive black holes at the centers of active galaxies
c) Compact sources of light at great distances
d) More common in the early universe than they are today
e) All of the above are correct
e) All of the above are correct
97
An appropriate label for the vertical (y) axis of the HR diagram would be _____.
a) Distance
b) Luminosity
c) Temperature
d) Size
b) Luminosity
98
There are more active galaxies, galaxy collisions, and galaxy interactions today than there were in the early universe.
a) True
b) False
b) False
99
Measurements of galaxy motions show that the universe is expanding. Measurements also show that Andromeda is getting closer to the Milky Way and should eventually collide with us. How can both of these statements be true?
a) Expansion only happens in the very distant universe.
b) Andromeda has the largest peculiar velocity of any galaxy and therefore is unaffected by expansion.
c) As seen from the Milky Way, Andromeda’s peculiar velocity is larger than its expansion velocity.
d) Andromeda and the Milky Way are becoming larger due to the expansion of the universe, thereby shrinking the distance between them.
c) As seen from the Milky Way, Andromeda’s peculiar velocity is larger than its expansion velocity.
100
What type of galaxy is the Milky Way?
a) Elliptical
b) Spiral or Barred Spiral
c) Irregular
d) Nobody knows because we are located inside, and can’t look out.
b) Spiral or Barred Spiral
101
Our solar system is approximately _______ from the center of the Milky Way.
a) 4.3 pc
b) 8 kpc
c) 30 to 40 kpc
d) 1 Mpc
e) 13.7 Mpc
b) 8 kpc
102
T/F Open clusters and young stars are generally found only in the disk of the galaxy and not in the halo.
True.
103
Which star has the shortest main sequence lifetime?
a) A 05. solar mass star
b) A 1 solar mass star
c) A 10 solar mass star
d) A 20 solar mass star
d) A 20 solar mass star
104
How much electrical charge does an atom with 6 protons, 6 neutrons, and 5 electrons have?
A) a total charge of +17
B) a negative charge of -5
C) a positive charge of +7
D) a positive charge of +1
E) none of the above
D) a positive charge of +1
105
An atom of the element iron has an atomic number of 26 and an atomic weight of 56. If it is neutral, how many protons, neutrons, and electrons does it have?
A) 26 protons, 30 neutrons, 26 electrons
B) 26 protons, 30 neutrons, 30 electrons
C) 26 protons, 56 neutrons, 26 electrons
D) 13 protons, 43 neutrons, 13 electrons
E) 13 protons, 56 neutrons, 13 electrons
A) 26 protons, 30 neutrons, 26 electrons
106
If you heat a gas so that collisions are continually bumping electrons to higher energy levels, when the electrons fall back to lower energy levels the gas produces:
A) thermal radiation.
B) an absorption line spectrum.
C) an emission line spectrum.
D) X rays.
E) radio waves.
C) an emission line spectrum.
107
When an electron in an atom goes from a higher energy state to a lower energy state, the atom:
A) emits a photon of a specific frequency.
B) absorbs a photon of a specific frequency.
C) absorbs several photons of a specific frequency.
D) can emit a photon of any frequency.
E) can absorb a photon of any frequency.
A) emits a photon of a specific frequency.
108
When white light passes through a cool cloud of gas, we see:
A) visible light.
B) infrared light.
C) thermal radiation.
D) an absorption line spectrum.
E) an emission line spectrum.
D) an absorption line spectrum.
109
Which of the following objects is not a close approximation of a thermal emitter?
A) hot, thin gas
B) a star
C) a filament in a light bulb
D) you
E) a planet
A) hot, thin gas
110
If two objects are the same size but one object is 3 times hotter than the other object, the hotter object emits:
A) 3 times more energy.
B) 9 times more energy.
C) 12 times more energy.
D) 81 times more energy.
E) none of the above
D) 81 times more energy.
111
The spectra of most galaxies show redshifts. This means that their spectral lines:
A) always are in the red part of the visible spectrum.
B) have wavelengths that are longer than normal.
C) have wavelengths that are shorter than normal.
D) have a higher intensity in the red part of the spectrum.
E) have normal wavelengths, but absorption of light makes them appear red
B) have wavelengths that are longer than normal.
112
From laboratory measurements, we know that a particular spectral line formed by hydrogen appears at a wavelength of 486.1 nanometers (nm). The spectrum of a particular star shows the same hydrogen line appearing at a wavelength of 485.9 nm. What can we conclude?
A) The star is moving toward us.
B) The star is moving away from us.
C) The star is getting hotter.
D) The star is getting colder.
E) The "star" actually is a planet.
A) The star is moving toward us.
113
Suppose the angular separation of two stars is smaller than the angular resolution of your eyes. How will the stars appear to your eyes?
A) You will not be able to see these two stars at all.
B) The two stars will look like a single point of light.
C) The two stars will appear to be touching, looking rather like a small dumbbell.
D) You will see two distinct stars.
E) You will see only the larger of the two stars, not the smaller one
B) The two stars will look like a single point of light.
114
Which of the following statements best describes the two principal advantages of telescopes over eyes?
A) Telescopes can collect far more light with far better angular resolution.
B) Telescopes can collect far more light with far greater magnification.
C) Telescopes have much more magnification and better angular resolution.
D) Telescopes collect more light and are unaffected by twinkling.
E) Telescopes can see farther without image distortion and can record more accurate colors.
A) Telescopes can collect far more light with far better angular resolution.
115
What do we mean by the diffraction limit of a telescope?
A) It is the maximum size to which any telescope can be built.
B) It describes the farthest distance to which the telescope can see.
C) It describes the maximum exposure time for images captured with the telescope.
D) It is the best angular resolution the telescope could achieve with perfect optical quality and in the absence of atmospheric distortion.
D) It is the best angular resolution the telescope could achieve with perfect optical quality and in the absence of atmospheric distortion.
116
What is meant by spectral resolution?
A) It is a measure of how much energy an object emits in different parts of the electromagnetic spectrum.
B) It is a measure of how close two spectral lines can be distinguished.
C) It is a measure of how close two point sources can be distinguished.
D) It is the same as angular resolution when applied to telescopes operating at different wavelengths.
B) It is a measure of how close two spectral lines can be distinguished.
117
A larger telescope will always have a higher spectral resolution than a smaller telescope when observing at the same wavelength.
True or False?
False.
118
Which of the following characteristics of a single star (one that moves through space alone) is it difficult to measure directly?
a) its apparent brightness
b) its temperature
c) its chemical composition
d) its mass
e) you can't fool me, all of these are quite easy to measure directly
d) its mass
119
You observe a star with B-V < 0. Is this star hotter or cooler than Vega? (Assume there is no extinction.)
Hotter.
120
Suppose you see two main-sequence stars of the same spectral type. Star 1 is dimmer in apparent brightness than Star 2 by a factor of 100. What can you conclude? (Neglect any effects that might be caused by interstellar dust and gas.)
a) Without first knowing the distances to these stars, you cannot draw any conclusions about how their true luminosities compare to each other.
b) The luminosity of Star 1 is a factor of 100 less than the luminosity of Star 2.
c) Star 1 is 100 times more distant than Star 2.
d) Star 1 is 100 times nearer than Star 2.
e) Star 1 is 10 times more distant than Star 2.
e) Star 1 is 10 times more distant than Star 2.
121
A planetary nebula is:
a) another term for the disk of gas around a young star that forms planets.
b) the cloud from which protostars form.
c) a shell of gas ejected from a low mass (M < 7M sun) star late in its life.
d) what is left when a white dwarf star explodes as a supernova.
e) the remnants of the explosion created by the collapse of the white dwarf's iron core.
c) a shell of gas ejected from a low mass (M < 7M sun) star late in its life.
122
How does a 1.2M sun white dwarf compare to a 1.0M sun white dwarf?
a) it has a larger radius.
b) it has a smaller radius.
c) it has a higher surface temperature.
d) it has a lower surface temperature.
e) it is supported by neutron, rather than electron, degeneracy pressure.
b) it has a smaller radius.
123
The white dwarf that remains when our Sun dies will be mostly made of:
a) hydrogen.
b) helium.
c) carbon.
d) neutrons.
c) carbon.
124
Observations show that elements with atomic mass numbers divisible by 4 (such as oxygen-16, neon-20, and magnesium-24) tend to be more abundant in the universe than elements with atomic mass numbers in between. Why do we think this is the case?
a) The apparent pattern is thought to be a random coincidence.
b) Elements with atomic mass numbers divisible by 4 tend to be more stable than elements in between.
c) At the end of the life of a higher-mass star new elements formed through a series of alpha particle capture reactions.
d) This pattern in elemental abundances was apparently determined during the first few minutes after the Big Bang.
c) At the end of the life of a higher-mass star new elements formed through a series of alpha particle capture reactions.
125
The vast majority of stars in a newly formed cluster are:
a) very high-mass, type O and B stars.
b) red giants.
c) about the same mass as our Sun.
d) less massive than the Sun.
d) less massive than the Sun.
126
A 10-solar-mass main-sequence star will produce which of the following:
a) white dwarf
b) neutron star
c) black hole
d) none of the above
b) neutron star
127
The most massive stars generate energy at the end of their lives by fusing iron in their cores.
True or False?
False.
128
What do we mean by the interstellar medium?
a) The gas and dust that lies in between stars in the Milky Way Galaxy.
b) The dust that fills the halo of the Milky Way Galaxy.
c) The middle section of the Milky Way Galaxy.
d) The name of an oracle who can channel messages from beings that live near the star called Vega.
a) The gas and dust that lies in between stars in the Milky Way Galaxy.
129
Which of the following is closest in size (radius) to a neutron star?
a) Earth
b) a city
c) a football stadium
d) a basketball
e) the Sun
b) a city
130
The Schwarzschild radius of a black hole depends on:
a) the observationally measured radius of the black hole.
b) the way in which the black hole formed.
c) only the mass of the black hole.
d) both the mass and chemical composition of the black hole.
c) only the mass of the black hole.
