Astro Test 2 Flashcards
A high-luminosity star …
A: is always at a larger distance than a low-luminosity star
B: emits more light than a low-luminosity star
C: is always redder than a star with a lower luminosity
D: is at a lower temperature than a low-luminosity star
E: is always at a smaller distance than a low-luminosity star
B
If a red giant appears the same brightness as a red main sequence star, which one is
farther away?
A: the red giant
B: we cannot tell
C: it depends on the phase of the Moon
D: the main sequence star
E: they are at the same distance
A
The heaviest nuclei of all are formed …
A: during helium burning
B: as part of the p-p chain
C: during carbon burning
D: during a supernova explosion
E: during all stages of stellar evolution of massive stars
D
Fill in the blank in the following chemical reaction that occurs in the Sun:
Hydrogen-2 + proton = _____ + energy:
A: Hydrogen-2
B: Hydrogen-1
C: Helium-3
D: Carbon-12
E: Helium-4
C
- Which of the following has the smallest radius?
A: type A main sequence star
B: main sequence star with surface temperature 8000 K
C: type K main sequence star
D: white dwarf
E: neutron star
E
Why does the main sequence part of a star’s life end?
A: The Helium in the core is exhausted.
B: The gravitational force is no longer large enough to balance the pressure.
C: The Hydrogen in the core is exhausted.
D: The temperature drops so that nuclear reactions are no longer possible.
E: Much of the mass of the star has evaporated.
C
Which of the following will have the shortest lifetime on the main sequence?
A: main sequence star with surface temperature 20000 K
B: main sequence star with surface temperature 3000 K
C: main sequence star with luminosity one tenth that of the Sun
D: the Sun
E: main sequence star with mass 2 times the Sun’s
A
Many of the brightest 100 stars viewed from Earth are not on the main sequence
(even though most stars are) because …
A: only high mass stars formed near to us in the Galaxy.
B: the most luminous stars are giants and supergiants that have already
finished their main sequence lifetimes.
C: our region of the Galaxy is very young.
D: the main sequence is the shortest part of a star’s life so stars do not spend
much time there.
E: our region of the Galaxy is very old.
B
A 2-solar-mass main sequence star is at the same distance as a 0.2-solar-mass main
sequence star. Which star appears brighter?
A: depends on the phase of the Moon
B: the 2 solar mass main sequence star appears brighter
C: the stars are approximately the same brightness
D: the 0.2 solar mass main sequence star appears brighter
E: we cannot tell with the information given
B
The temperature of the photosphere of the Sun is closest to …
A: 10^7 Kelvin
B: 10^6 Kelvin
C: 100 Kelvin
D: 600,000 Kelvin
E: 6000 Kelvin
E
An estimate of the number of communicating / technological civilizations that we
expect in our Galaxy would be a larger number if …
A: the average lifetime of a communicating civilization were smaller
B: the star formation rate in our Galaxy were smaller
C: the average number of planets that could support life for each star were larger
D: it were more difficult for life to develop intelligence, once life had formed
E: a smaller percentage of stars formed planets
C
If the Sun had twice its mass, then which of these planets would be in its habitable
zone?
A: Mercury
B: Venus
C: Earth
D: Neptune
E: Jupiter
E
What is the exoplanet’s orbital period, and the percent brightness drop in light, for
the case in the image above from the Kepler Exoplanet Transit Hunt activity?
A: 60 days and 0.15 %
B: 20 days and 0.15 %
C: 10 days and 0.15 %
D: 5 days and 0.30 %
E: 60 days and 0.30 %
D
How do astronomers measure the temperature of stars?
A: The inverse square law is used.
B: Temperature is determined from the radius of the star that is measured by
radar.
C: By looking at which absorption lines are present in the star’s spectrum.
D: The rate of change of the color of the star is measured.
E: By comparing the luminosity and apparent brightnesses.
C
In the inverse square law activity above, what would the wattage of the top
lightbulb need to be, such that it appeared as bright as the bottom lightbulb which
is a 25-Watt bulb?
A: 400 Watts
B: 100 Watts
C: 50 Watts
D: 25 Watts
E: 20 Watts
B
The largest fraction of nearby stars (e.g., within 100 light years) are …
A: neutron stars
B: Sun-like stars
C: blue main sequence stars
D: red main sequence stars
E: blue supergiants
D
Which of the stars, in the diagram above, is the hottest?
A: A
B: B
C: C
D: D
E: E
D
If they were all formed at the same time, which of the stars in the diagram above
will live the longest?
A: A
B: B
C: C
D: D
E: E
B
The parallax angle of a nearby star is measured to be 0.02 arcseconds. What is the
distance to the star?
A: 20 parsecs
B: 2 light years
C: 50 parsecs
D: 0.2 light years
E: 200 light years
C
Which of the following is the sequence of events for a 40-solar mass star
(one of the most-massive stars)?
A: planetary nebula, protostar, Sun-like star on main sequence, blue giant,
red giant
B: stellar nursery, protostar, Sun-like star on main sequence, red giant,
planetary nebula, white dwarf
C: stellar nursery, blue giant, Sun-like star on main sequence, red giant,
Type II supernova, neutron star
D: stellar nursery, protostar, blue star on main sequence, Type II supernova,
black hole
E: black hole, neutron star, white dwarf, Sun-like star on main sequence,
red giant, Type II supernova
D
Star A is 9 times as luminous as Star B. The two stars appear the same brightness.
What is true about their distances?
A: Star A is 9 times farther away than Star B.
B: Star B is 9 times farther away than Star A.
C: Star A is 3 times farther away than Star B.
D: Star B is 3 times farther away than Star A.
E: Stars A and B are at the same distance.
C
In the p-p chain, shown in the above diagram, what particles must be input in order
to produce one 4He nucleus?
A: 8 protons, but 2 of them are returned when the 4He is produced
B: 6 protons, but 2 of them are returned when the 4He is produced
C: 2 photons and 2 positrons
D: 2 protons and 4 neutrons
E: 4 neutrons
B
What is the name of the slightly cooler layer of the Sun just outside the
photosphere?
A: core
B: corona
C: convective zone
D: chromosphere
E: radiative zone
D
How does a star move on the H-R diagram during the period of time it is converting
hydrogen to helium in its core?
A: It moves from the far lower right corner of the diagram to the far upper left
corner of the diagram, along the main sequence.
B: It moves from the upper left of the diagram to the lower right of the diagram,
along the main sequence.
C: It remains nearly fixed at a certain point on the main sequence and does
not move on the H-R diagram.
D: It moves from the upper right of the diagram to the lower left of the diagram.
E: It moves from the lower left of the diagram to the upper right of the diagram
C
If the entire mass of Earth were concentrated in a region the size of a marble, the
resulting object would be …
A: a Sun-like star
B: a white dwarf
C: a neutron star
D: a black hole
E: a planetary nebula
D
Which is the smallest object?
A: a neutron star
B: the Solar System
C: the Sun
D: a dwarf galaxy
E: the Eagle nebula
A
A galaxy has an H-alpha emission line observed at a wavelength 10 percent larger
than the rest wavelength of H-alpha. What is the redshift of the galaxy?
A: 10
B: 0.001
C: 0.1
D: 1
E: -0.001
C
What is in this image? (right)
A: supernova remnant
B: irregular galaxy
C: planetary nebula
D: globular star cluster
E: star forming region
A
Which is the most luminous?
A: nova
B: supernova
C: quasar
D: the Sun
E: white dwarf
C
Which contains the most stars?
A: an open star cluster
B: a globular star cluster
C: a spiral galaxy
D: the Solar System
E: the alpha Centauri star system
C
Galaxy A appears twice the angular size of Galaxy B. Assuming the two galaxies
have the same physical size in kiloparsecs, which of the following is true?
A: Galaxy A is 2 times farther away than Galaxy B.
B: Galaxy B is 2 times farther away than Galaxy A.
C: Galaxy A and B are at the same distance.
D: Galaxy A is 4 times farther away than Galaxy B.
E: Galaxy B is 4 times farther away than Galaxy A.
B
What fundamental particles make up a Helium-3 atom?
A: 2 up quarks, 1 down quark, 1 electron
B: 6 up quarks, 6 down quarks, 2 electrons
C: 3 up quarks, 3 down quarks, 3 electrons
D: 1 proton, 2 neutrons, 1 electron
E: 5 up quarks, 4 down quarks, 2 electrons
E
In what box does the galaxy in the bottom center belong in this Hubble tuning fork
diagram?
A: E1
B: Irr
C: Sc
D: SBb
E: SBc
D
Which statement is FALSE?
A: planetary nebulae can have layers because of pulsating stars
B: planetary nebulae usually last tens of thousands of years
C: a planetary nebula will be part of the end state of the Sun
D: planetary nebulae usually have black holes at their centers
E: planetary nebulae are a few light years in size
D
Which statement is TRUE?
A: Stars form in molecular clouds, where temperatures are about 10 Kelvin.
B: A cloud will collapse and form stars if its mass is a lot less than its Jeans mass.
C: A nova outburst typically only happens once in a star’s life.
D: Stars usually form in isolation, far away from other stars
E: The Crab supernova, in our galaxy, went off about 8 years ago.
A
How tiny a spot is the Hubble Deep Field?
A: About 1/2 of the entire sky.
B: About 1/5 of the entire sky.
C: About 1/10 of the entire sky.
D: About 1/50 of the entire sky.
E: The size of President Roosevelt’s eye on a dime held at arm’s length.
E
Among these choices, what is the last thing that happens in the history of the Universe?
A: electrons join with nuclei to make atoms
B: quarks join together to make protons and neutrons
C: nucleosynthesis
D: the Planck epoch
E: the Big Bang expansion begins
A
If a galaxy had no dark matter, we would observe …
A: the entire galaxy would approach us at a faster velocity, and we would
observe a redshift
B: the entire galaxy would recede from us at a faster velocity, and we would
observe a redshift
C: the rotation velocity would remain constant with increasing distance
D: the rotation velocity would decrease with increasing distance like the
Keplerian curve in our Solar System
E: the rotation velocity would increase with increasing distance like the
Keplerian curve in our Solar System
D
How many times bigger is the Local Group of galaxies in which the Milky Way
resides than the Milky Way itself?
A: it is not bigger than the Milky Way
B: about 100 times bigger
C: about 1040 times bigger
D: about 1010 times bigger
E: about 1 million times bigger
B
Which one of the following is FALSE?
A: Irregular galaxies, although small, often have a lot of star formation taking
place in them.
B: Barred spiral galaxies have similar properties to normal spirals, except for
the “bar” feature.
C: Galaxy collisions destroy most of the stars in the galaxies involved.
D: Most galaxies appear to be receding from the Milky Way Galaxy.
E: Most elliptical galaxies contain only old stars.
C
If a galaxy is moving away from us the wavelength of the light it emits will be …
A: unaffected.
B: blueshifted.
C: increased.
D: decreased.
E: distorted.
C
The stars in the halo of our Milky Way Galaxy are …
A: in a very flat distribution.
B: very close together compared to stars in the disk.
C: older and bluer than those in the disk.
D: never in globular clusters.
E: older and redder than those in the disk.
E
The supermassive black hole in the center of the Milky Way has a mass of …
A: 10 solar masses
B: 1,000 solar masses
C: 4 million solar masses
D: 100 billion solar masses
E: 100 solar masses
C
In the figure above, how would you calculate the fraction of the mass of the gas
in the universe that is in the form of Helium?
A: take 4×4 for the mass of Helium, and divide by 4×4 + 48×1 for the total mass
B: take 4×1 for the mass of Helium, and divide by 48×1 for mass of Hydrogen
C: take 4 for the mass of Helium, and divide by 48 for the mass of Hydrogen
D: take 48×1 for the mass of Hydrogen, and divide by 4×4 + 48×1 for total mass
E: take 48×4 for the mass of Hydrogen, and divide by 4×1 + 48×4 for total mass
A
Which force has the photon as its boson?
A: strong
B: weak
C: electromagnetic
D: gravity
E: none of the forces do
C
Which mysterious phenomena do scientists attribute to dark energy?
A: The increasing rate of expansion of the Universe.
B: Mysterious bonding that holds atoms together.
C: The creation of the cosmic microwave background.
D: The formation of Helium through nucleosynthesis.
E: Dark energy causes all of the above.
A
Why can we NOT see back the whole way to the time Big Bang expansion began?
A: Not enough photons were produced.
B: Radiation is blueshifted out of the visible range.
C: Our telescopes could never be powerful enough.
D: The radiation scatters off matter frequently so the Universe is opaque.
E: It would take too long for light to travel that far.
D
What are the “standard candles” that were used to determine the Universe is
accelerating?
A: spiral galaxies
B: elliptical galaxies
C: Type Ia supernovae
D: light bulbs
E: Type II supernovae
C
An older star cluster …
A: contains hotter stars than a younger star cluster.
B: has a main sequence turnoff farther to the left on the H-R diagram.
C: has a main sequence turnoff farther to the right on the H-R diagram.
D: would never be located in the halo of a galaxy.
E: has a bluer color than a younger star cluster.
C
Which of the following statements is TRUE?
A: One or two supernova are observed to go off in the Milky Way galaxy
each year.
B: Type II supernovae are produced by the death of a massive star.
C: Type Ia supernovae show a lot of strong hydrogen lines in their spectra.
D: Type Ia supernovae are produced when a neutron star collapses to become a
black hole.
E: When a planetary nebula is produced it can outshine an entire galaxy.
B
What is the proton-proton chain
a long-lasting source of energy in stars: 4 protons combine to make helium-4
(2 protons and 2 neutrons) and release energy in gamma rays
Step 1 on p-p chain
two protons collide at very high speed, and stick together;
one of them changes into a neutron; ends with a Deuterium nucleus
( 2H : 1 proton and 1 neutron, bound together), plus released energy
Step 2 of p-p chain
euterium nucleus from Step 1 collides with another proton, and makes
a Helium-3 nucleus ( 3He : 2 protons and 1 neutron, bound together),
plus some more excess energy released
Step 3 of p-p chain
wo Helium-3 nuclei combine to make a Helium-4 nucleus
( 4He : 2 protons and 2 neutrons, bound together),
releasing back 2 protons in the process and some more extra energy
Layer of sun: at the center; high density and temperature; where nuclear reactions occur
and gamma rays are produced
core
Layer of sun: hotons are repeatedly re-absorbed and re-emitted; the energy of
an individual photon can take on average 170,000 years to pass through
radiative zone
Layers of sun: hot gas rises and cold gas sinks; light traverses in about 1 week
convective zone
Layers of sun: mperature 5,780 K; this is the “surface” of the Sun that we see;
photons have been converted to visible wavelengths; can see “granules” due
to convection bringing material up and down in cells
photosphere
Layers of sun: red or orange color; temperature about 4,500 K; we see through
this, down to the photosphere
chromosphere
Layers of sun: an eruption coming out of Sun due to magnetic activity
flare
Layers of sun: hoop-shaped eruption out of Sun due to magnetic activity
prominence
Layers of sun: ow density; temperature about 1 million K; visible during solar eclipses
corona
Layers of sun: charged particles coming from Sun’s surface, escaping to deep space; permeates the whole Solar System
3
solar wind
Inverse square law
B = L/4𝝅d^2 or B=L / d^2
