Final Exam

Question 1

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.

Answer 1

False.

Question 2

Who is the astronomer indicated by the “H” in the H-R diagram?

a) Hubble
b) Henry
c) Hertzsprung
d) Huggins
e) Hoyle

Answer 2

c) Hertzsprung

Question 3

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

Answer 3

d) M

Question 4

Which type of star has the strongest Balmer lines of hydrogen?

a) A
b) B
c) G
d) M
e) O

Answer 4

a) A

Question 5

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

Answer 5

a) Annie Jump Cannon

Question 6

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.

Answer 6

e) All of the above are true.

Question 7

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

Answer 7

b) 6

Question 8

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

Answer 8

c) Upper left

Question 9

The spectral sequence in order of decreasing temperature is:

a) OFBAGKM
b) OBAGFKM
c) OBAFGKM
d) ABFGKMO
e) BAGFKMO

Answer 9

c) OBAFGKM

Question 10

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

Answer 10

d) The orbital period of the planet

Question 11

Cluster ages can be determined from:

a) main sequence fitting
b) main sequence turnoff
c) pulsating variable stars
d) spectroscopic binaries
e) visual binaries

Answer 11

b) main sequence turnoff

Question 12

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

Answer 12

b) millions of degrees

Question 13

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

Answer 13

a) it predicted that the Sun could last only about 25 million years, which is far less than the age of Earth

Question 14

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

Answer 14

c) outward pressure and gravity

Question 15

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

Answer 15

c) when the Sun was being formed from a collapsing cloud of gas

Question 16

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

Answer 16

d) there is a balance within the Sun between the outward push of pressure and the inward pull of gravity

Question 17

How does the Sun generate energy today?

a) nuclear fission
b) nuclear fusion
c) chemical reactions
d) gravitational contraction
e) gradually expanding in size

Answer 17

b) nuclear fusion

Question 18

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

Answer 18

d) 100 million K

Question 19

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

Answer 19

a) they are both very hot and very small

Question 20

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

Answer 20

d) a few tons

Question 21

Which of the following is closest in mass to a white dwarf?

a) the Moon
b) Earth
c) Jupiter
d) Neptune
e) the Sun

Answer 21

e) the Sun

Question 22

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

Answer 22

b) a white dwarf

Question 23

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

Answer 23

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

Question 24

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

Answer 24

a) an object for which we are likely to know the true luminosity

Question 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

Answer 25

d) mass they are formed with

Question 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

Answer 26

e) protostar, main-sequence, red giant, white dwarf

Question 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?

Answer 27

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.

Question 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?

Answer 28

atomic number = 26
atomic mass number = 56
number of electrons = 26

Question 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?

Answer 29

Atoms 2 and 3 are isotopes.

Question 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.

Answer 30

O+5 is 5x ionized
3e-
OVI

Question 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.

Answer 31

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.

Question 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.

Answer 32

e) the radius of a body at which its escape velocity equals the speed of light.

Question 33

Which kinds of stars are most common in a newly formed star cluster?

a) O stars
b) G stars
c) M stars

Answer 33

c) M stars

Question 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

Answer 34

c) about a micrometer or less; silicates and carbon compounds

Question 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.

Answer 35

b) 70% Hydrogen, 28% Helium, 2% heavier elements.

Question 36

The most abundant molecule in molecular clouds is:
a) H2
b) He2
c) CO
d) H2O
e) HHe

Answer 36

a) H2

Question 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

Answer 37

b) from 1 million years for the most massive stars up to 100 million years for the least massive stars

Question 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

Answer 38

b) 80 times the mass of Jupiter

Question 39

What are the letters that follow the spectral sequence OBAFGKM?

a) NP
b) YZ
c) LT
d) CD
e) UV

Answer 39

c) LT

Question 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.

Answer 40

d) 150 solar masses.

Question 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

Answer 41

d) iron

Question 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.

Answer 42

c) The core contracts and becomes a black hole.

Question 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

Answer 43

c) the sudden collapse of an iron core into a compact ball of neutrons

Question 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.

Answer 44

d) a very massive main-sequence star.

Question 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.

Answer 45

b) As the star spins, beams of radio radiation sweep through space. If one of the beams crosses Earth, we observe a pulse.

Question 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.

Answer 46

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.

Question 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.

Answer 47

c) The spectrum of a massive-star supernova shows prominent hydrogen lines, while the spectrum of a white-dwarf supernova does not.

Question 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.

Answer 48

e) Either a neutron star or a black hole.

Question 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.

Answer 49

c) Any object from which the escape velocity exceeds the speed of light.

Question 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.

Answer 50

a) It will cool down and become a cold black dwarf.

Question 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.

Answer 51

c) When nuclear fusion begins in the core.

Question 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.

Answer 51

c) Interstellar dust absorbs more blue light than red light, making stars appear redder than their true color.

Question 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.

Answer 51

c) Infrared.

Question 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.

Answer 52

d) It will slow down, the magnetic field will weaken, and it will become invisible.

Question 53

Levels of the Sun’s composition:

Answer 53

Core
Radiation Zone
Convection Zone
Photosphere
Chromosphere
Corona
Solar Wind

Question 54

The Sun is located in the _______ of the Milky Way.

a) Nuclear bulge
b) Center
c) Spheroid
d) Halo
e) Disk

Answer 54

e) Disk

Question 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.

Answer 55

c) formed more recently and have therefore been made from enriched stellar gas.

Question 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

Answer 56

a) atomic hydrogen

Question 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

Answer 57

e) all of the above

Question 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.

Answer 58

c) Globular cluster ages increase with distance from the Milky Way.

Question 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

Answer 59

a) velocity and distance

Question 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.

Answer 60

c) Interstellar dust absorbs more blue light than red light, making stars appear redder than their true color.

Question 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.

Answer 61

d) 150 solar masses.

Question 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

Answer 62

a) Barred Elliptical

Question 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

Answer 63

a) Moving toward us

Question 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

Answer 64

c) infrared

Question 65

Elliptical galaxies typically contain lots of gas and dust and are sites of active star formation.

a) True
b) False

Answer 65

b) False

Question 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.

Answer 66

e) both (b) and (c) are correct.

Question 67

The length of time a star spends fusing hydrogen into helium is called its main sequence lifetime.

a) True
b) False

Answer 67

a) True

Question 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

Answer 68

a) A failed star; its mass is too small for nuclear fusion to ever occur

Question 69

A planetary nebula (e.g., the Ring nebula) is a region of planetary formation around a star.

a) True
b) False

Answer 69

b) False

Question 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

Answer 70

d) Interstellar cloud, protostar, main sequence star, red giant, planetary nebula and white dwarf

Question 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)

Answer 71

e) Iron (Fe)

Question 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

Answer 72

e) Annie Cannon

Question 73

A pulsar is a(n):

a) Black hole
b) Rotating neutron star
c) Rotating white dwarf
d) Oscillating black hole
e) Oscillating protostar

Answer 73

b) Rotating neutron star

Question 74

The spectral sequence (classes) in order from hottest to coolest is:

a) OABFGKM
b) OBAGFKM
c) MKGFBAO
d) OBAFGKM
e) MKFGABO

Answer 74

d) OBAFGKM

Question 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

Answer 75

b) Vega

Question 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.

Answer 76

b) Star B

Question 77

Low mass stars (1 solar mass and below) are more common than high mass stars.

a) True
b) False

Answer 77

a) True

Question 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

Answer 78

a) Rigel

Question 79

An ‘M’ main sequence star is more massive than an ‘A’ main sequence star.

a) True
b) False

Answer 79

b) False

Question 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

Answer 80

c) Arcturus

Question 81

White dwarf stars in binary star systems have the possibility of becoming Novae.

a) True
b) False

Answer 81

a) True

Question 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

Answer 82

c) It would only be 1/9 as bright

Question 83

Population I stars are found primarily in the disks and spiral arms of galaxies.

a) True
b) False

Answer 83

a) True

Question 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

Answer 84

a) The smaller star

Question 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

Answer 85

a) True

Question 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

Answer 86

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

Question 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

Answer 87

a) True

Question 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

Answer 88

b) Type II

Question 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

Answer 89

b) An electron jumps from a higher to a lower energy level

Question 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.

Answer 90

a) Betelgeuse.

Question 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

Answer 91

a) More affected by interstellar extinction

Question 92

The Sloan Digital Sky Survey (SDSS) has measured distances to over one million galaxies.

a) True
b) False

Answer 92

a) True

Question 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.

Answer 93

d) Have a hot interior that shines through a cooler, low-density gas.

Question 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.

Answer 94

c) Discovered the existence of Cepheid variables and their period-luminosity relationship.

Question 95

Distant galaxies have higher recessional velocities is a ____ statement about the expansion of the universe.

a) True
b) False

Answer 95

a) True

Question 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

Answer 96

e) All of the above are correct

Question 97

An appropriate label for the vertical (y) axis of the HR diagram would be _____.

a) Distance
b) Luminosity
c) Temperature
d) Size

Answer 97

b) Luminosity

Question 98

There are more active galaxies, galaxy collisions, and galaxy interactions today than there were in the early universe.

a) True
b) False

Answer 98

b) False

Question 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.

Answer 99

c) As seen from the Milky Way, Andromeda’s peculiar velocity is larger than its expansion velocity.

Question 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.

Answer 100

b) Spiral or Barred Spiral

Question 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

Answer 101

b) 8 kpc

Question 102

T/F Open clusters and young stars are generally found only in the disk of the galaxy and not in the halo.

Answer 102

True.

Question 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

Answer 103

d) A 20 solar mass star

Question 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

Answer 104

D) a positive charge of +1

Question 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

Answer 105

A) 26 protons, 30 neutrons, 26 electrons

Question 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.

Answer 106

C) an emission line spectrum.

Question 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.

Answer 107

A) emits a photon of a specific frequency.

Question 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.

Answer 108

D) an absorption line spectrum.

Question 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

Answer 109

A) hot, thin gas

Question 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

Answer 110

D) 81 times more energy.

Question 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

Answer 111

B) have wavelengths that are longer than normal.

Question 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.

Answer 112

A) The star is moving toward us.

Question 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

Answer 113

B) The two stars will look like a single point of light.

Question 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.

Answer 114

A) Telescopes can collect far more light with far better angular resolution.

Question 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.

Answer 115

D) It is the best angular resolution the telescope could achieve with perfect optical quality and in the absence of atmospheric distortion.

Question 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.

Answer 116

B) It is a measure of how close two spectral lines can be distinguished.

Question 117

A larger telescope will always have a higher spectral resolution than a smaller telescope when observing at the same wavelength.

True or False?

Answer 117

False.

Question 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

Answer 118

d) its mass

Question 119

You observe a star with B-V < 0. Is this star hotter or cooler than Vega? (Assume there is no extinction.)

Answer 119

Hotter.

Question 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.

Answer 120

e) Star 1 is 10 times more distant than Star 2.

Question 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.

Answer 121

c) a shell of gas ejected from a low mass (M < 7M sun) star late in its life.

Question 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.

Answer 122

b) it has a smaller radius.

Question 123

The white dwarf that remains when our Sun dies will be mostly made of:

a) hydrogen.
b) helium.
c) carbon.
d) neutrons.

Answer 123

c) carbon.

Question 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.

Answer 124

c) At the end of the life of a higher-mass star new elements formed through a series of alpha particle capture reactions.

Question 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.

Answer 125

d) less massive than the Sun.

Question 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

Answer 126

b) neutron star

Question 127

The most massive stars generate energy at the end of their lives by fusing iron in their cores.

True or False?

Answer 127

False.

Question 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.

Answer 128

a) The gas and dust that lies in between stars in the Milky Way Galaxy.

Question 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

Answer 129

b) a city

Question 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.

Answer 130

c) only the mass of the black hole.