Download Stellar Astronomy Sample Questions for Exam 3

Stellar Astronomy
Sample Questions for Exam 3
Chapter 7
1.
A protostar is formed by
a) the rapid expansion of gas from an exploding star.
b) the gravitational collapse of a rotating interstellar cloud.
c) the ignition of thermonuclear fusion in an expanding nebula.
d) the remnants of a red giant star.
2.
The angular momentum of an object does not depends on
a) the mass of the object.
b) how fast the object is rotating.
c) how the mass of the object is distributed.
d) the temperature of the object.
3.
In the nebular model for the formation of the solar system
a) the rocky planets form close to the sun.
b) the solar system forms from a giant cloud made almost entirely of dust.
c) the sun was formed much later than the planets and is thus younger.
d) the inner planets formed much earlier than the outer planets.
e) All of the above are part of the nebular theory.
4.
Which of the following statements is false?
a) As the solar nebula began to collapse under its own gravity it began to
spin-up due to the conservation of angular momentum.
b) As the solar nebula began to collapse under its own gravity it began to
flatten out into a disk shape with a central bulge.
c) Protoplanetary disks (proplyds) are infant solar systems in the process
of forming.
d) The protosun produced energy by fusing hydrogen in its core.
5.
Accretion is
a) the sticking of small particles to form larger particles.
b) the growth of particles by condensation of gas.
c) the flattening out of a rotating disc of material as it shrinks.
d) the spinning up of a rotating disk as it shrinks in size.
6.
Planetesimals form by
a) accretion first then condensation.
b) condensation first then accretion.
c) only by condensation.
d) only by accretion.
7.
In the nebular model of planetary formation
a) the highest density planets form closest to the sun and the lower
density planets form farther out.
b) the planets condense from a gas and dust nebula long before the sun
is formed.
c) the lowest density planets form closest to the sun and the higher
density planets form farther out.
d) the sun forms billions of years before the planets begin to form.
8.
The two types of leftovers planetesimals in the solar system are
a) terrestrial and Jovian.
b) comets and asteroids.
c) meteorites and meteoroids.
d) moons and stars.
9.
During the earliest times of the solar system
a) there were 4 terrestrial planets and four gas giants.
b) there were as many as 100 moon to Mars sized protoplanets in the
inner part of the solar system.
c) there were as many as 100 Uranus to Saturn sized protoplanets in the
outer solar system.
d) the solar system was dominated by two objects much larger in size
than Jupiter which collided, shattered and formed all the other planets.
e) None of the above, we have no idea what it was like in the earliest
times of the solar system.
10.
In the search for extra-solar planets the technique that has found the most
planets uses
a) the Doppler shift of the star to detect the wobble in the stars motion
caused by the presents of a planet.
b) direct observations of the side-to-side motion of the star caused by the
presence of a planet.
c) direct observations of the planets.
d) changes in the emission spectrum of the star due to the additional
emission lines from the planet.
11.
Of the extra-solar planets found around sun-like stars so far
a) almost all are Earth-like planets.
b) almost all are large planets like Jupiter.
c) there is an even mix of Earth-like and Jupiter-like planets.
d) all have been found in highly eccentric orbits that range from almost
skimming the surface of the star to over 100AU.
Short Answer Questions
1. Briefly describe the nebular model for the formation of the solar system.
Include details about the formation of both the central star and the planets
around it.
2. Describe some of the evidence we have for how we think solar systems
like ours form. Where do they form? What types of objects have been
observed? How do the observations compare to the nebular model of
solar system formation?
3. Describe the hunt for extra-solar planets. What kinds of techniques are
used, what kinds of planets have been found, how many planets have
been found, what kind of orbits do the planets have?
4. Most of the exoplanets that have been found are “hot Jupiter’s”: large gas
giants orbiting very close to their star. Explain why these types of planets
are easiest to find with the techniques astronomers use to find exoplanets
and why Earth sized planets are so hard to find. How has the nebular
theory for the formation of our solar system had to be modified to explain
these hot Jupiter’s?
Chapter 13
1.
Stellar parallax
a) can be accurately measured for stars less that 300 light-years away.
b) does not exist because the earth does not move in the heavens.
c) increases with the distance to the star.
d) is too small to measure even with the largest telescopes and the
closest stars.
2.
The parsec is defined as
a) the distance at which a star shows a parallax of one arcsecond.
b) the average distance between the earth and the sun.
c) the distance to the nearest star.
d) the distance light travels in one year.
3.
Stellar parallax is
a) the real motion of stars through the universe.
b) the distance unit used to measure the distance to planets.
c) the change in the position of a star due to change in seasons.
d) the apparent change in the direction of something due to a change in
vantage point of the observer.
4.
To determine the luminosity of a star we need
a) only the brightness of the star.
b) only the distance to the star.
c) both the brightness and the distance to the star.
d) None of the above.
5.
The color ratio of a star is
a) the ratio of the magnitude of the star observed through two different
color filters.
b) the ratio of the color of a star to its surface temperature.
c) the ratio of the color of a star to its diameter.
d) the ratio of the color of a star to the amount of interstellar reddening.
e) None of the above.
6.
The stellar spectra classification scheme classifies according to
a) the mass of the star.
b) the surface temperature of the star.
c) the diameter of the star.
d) the distance to the star.
e) None of the above.
7.
The absorption spectral lines of hydrogen are weaker for stars at the
lowest surface temperatures because
a) cooler stars have less hydrogen.
b) the hydrogen has sunk to a hotter level.
c) at low temperatures the hydrogen emits light instead of absorbing light
so there is no absorption spectrum.
d) at low temperatures all the hydrogen is in the ground state so no
electrons are in the excited states that are responsible for absorption.
e) None of the above, the coolest stars have the strongest hydrogen
absorption spectra.
8.
By spectral class, the hottest to coolest stars are
a) M, K, G, F, A, B & O
b) A, B, C, D, E, F & G
c) A, B, F, G, K, M & O
d) O, B, A, F, G, K & M
9.
The Hertzsprung-Russell diagram is
a) a plot of mass versus luminosity of stars.
b) a plot of luminosity versus temperature of stars.
c) a plot of luminosity versus distance of stars.
d) a plot of mass versus temperature of stars.
10.
On an H-R diagram, most stars lie in the region called the
a) main sequence.
b) subgiant sequence.
c) giant sequence.
d) supergiant sequence.
e) None of the above.
11.
On an H-R diagram, the stars in the top right corner are
a) supergiants.
b) white dwarfs.
c) main sequence.
d) red dwarfs.
12.
A binary star system is
a) a single star with a large planet orbiting it.
b) two stars of equal mass passing each other in space.
c) two stars in orbit around a common center of mass.
d) a star that switches on and off in binary code.
e) None of the above.
13.
Observing binary star systems is important because
a) they allow us to accurately determine the distance to stars.
b) they allow us to accurately measure the luminosity of stars.
c) they allow us to accurately measure the color index of stars.
d) they allow us to accurately determine the mass of stars.
e) None of the above, there is no special reason to observe binary star
systems.
14.
An eclipsing binary is one in which
a) both stars are easily visible to the naked eye.
b) the individual stars can only be identified by their spectra.
c) both stars can be resolved in a telescope.
d) the stars pass directly in front of each other, eclipsing each other.
e) None of the above.
15.
By studying eclipsing binaries we can determine
a) the individual spectra of both stars.
b) the diameters of both of the stars.
c) the masses of both of the stars.
d) All of the above.
Short Answer Questions
1. Explain why the distance to some stars can be determined by parallax but
most stellar distances cannot.
2. Describe the different properties of main sequence stars that are determined
by the mass of the star. Why is mass so important to the characteristics of a
star?
3. Why is it so important to study binary systems? What information can be
gained from them that can’t be otherwise? What properties of binary systems
allow us to determine this information and what laws of physics allow us to
find it?
Chapter 14
1.
The visible light we receive from the Sun
a) comes directly from the energy source at the Sun’s core.
b) is radiated from the solar photosphere.
c) is generated by solar flares.
d) is called the solar wind.
e) None of the above, we don’t receive any light from the Sun.
2.
The primary energy source in the Sun is
a) the fusion of hydrogen into helium in the core.
b) the burning of carbon (as coal) in the core.
c) the residual energy left over from gravitational collapse.
d) the fission of uranium into two smaller atoms in the core.
The proton-proton cycle is
a) the fusion of four hydrogen nuclei into a single helium nucleus plus two
positrons and energy through several steps.
b) the fusion of three helium nuclei into a single carbon nucleus through
several steps.
c) the fusion of two protons into a helium nucleus.
d) the emission of electromagnetic radiation due to a transition from one
energy level to another by a pair of protons.
e) None of the above.
3.
4.
Energy flows from the core of the Sun to the photosphere by
a) convection for 7/10 the distance then by radiation for the rest.
b) radiation for 7/10 the distance then by convection for the rest.
c) convection all the way.
d) radiation all the way.
5.
The interior structure of the Sun can be determined by.
a) placing seismograph detectors on the surface of the sun and observing
sound waves that are transmitted through the Sun.
b) direct observations using gamma ray radiation.
c) modeling the interior structure using computer programs then matching
the predictions to the observed properties at the surface.
d) diving down into the interior of the Sun in heavily shielded spacecraft.
6.
Early experiments to look for solar neutrinos found
a) about five times more neutrinos than were expected.
b) exactly as many neutrinos as were expected.
c) only about one third as many neutrinos as were expected.
d) less than one percent of the neutrinos that were expected.
e) None of the above, neutrinos cannot be detected.
7.
Modern experiments that look for solar neutrinos have found
a) about five times more neutrinos than are expected.
b) exactly as many neutrinos as are expected.
c) only about one third as many neutrinos as are expected.
d) less than one percent of the neutrinos that are expected.
e) None of the above, neutrinos cannot be detected.
8.
Which of the following statements is false?
a) The photosphere is composed of granules, each about 1000km
across, which are convection areas of rising and falling gas.
b) The chromosphere is composed of spicules that look like blades of
burning grass and are 700km across and up to 7,000km high.
c) The average temperature of the chromosphere is about 10,000°C.
d) The temperature in the chromosphere decreases with increasing
altitude.
9.
The chromosphere of the Sun is
a) hotter than the photosphere by several thousand degrees.
b) only visible for a brief instant before and after totality during a solar
eclipse.
c) composed of spicules that look like blades of burning grass.
d) studied by a Flash Spectrum taken during solar eclipses.
e) All of the above
10.
The corona of the Sun is
a) cooler than the surface of the Sun.
b) visible during a total solar eclipse and in x-rays.
c) the layer just below the photosphere of the Sun.
d) a uniform sphere surrounding the Sun.
11.
Sunspots occur on the sun
a) in 11 year cycles.
b) in the polar latitudes of the Sun.
c) singly with no magnetic polarity.
d) in areas of extremely weak magnetic fields.
12.
Sunspots are
a) hotter regions on the surface of the Sun.
b) cooler regions (by as much as 1500 °C on the surface of the Sun.
c) completely black regions where no light at all is produced.
d) regions of extremely weak magnetic fields.
13.
A butterfly diagram is
a) a diagram showing the change in number and latitude of sunspots with
time.
b) a diagram showing the change in the pattern colors on butterfly wings
with the sunspot cycle.
c) a diagram showing the change in color of sunspots during their 11 year
cycle.
d) a diagram showing the change in average life span of sunspots during
their 11 year cycle.
e) None of the above.
14.
Historically, the sunspot cycle has
a) been absolutely constant over all of recorded history.
b) changed dramatically almost every few decades.
c) changed gradually over the centuries with periods of low activity
corresponding to “little ice ages” here on Earth.
d) changed slowly over millennia with no observable influence on Earth’s
climate.
15.
A solar flare is
a) a long lived dark spot that appears on the surface of the Sun.
b) a large looped eruption of material from the area around sunspots that
follows the magnetic field lines and is about 10,000°C.
c) a bright area on the surface of the Sun surrounding sunspots.
d) a violent eruption of material from the area around sunspots that can
reach temperatures of 5,000,000°C or higher.
Short Answer Questions
1.
2.
3.
4.
5.
6.
7.
Describe the layers of the Sun beginning at the visible surface and moving
outward. What are the different layers called, how thick are they and what
are their temperatures.
Use words and a diagram to describe the interior structure of the Sun and
explain how energy flows from the core to the surface.
Describe the proton-proton cycle. What are the particles that start the
cycle, what are the particles that are produced and how is the energy
released?
Describe the photosphere of the Sun. What does it look like, how thick is
it, what is the temperature and how does it change with altitude and what
does its spectrum look like.
Describe sunspots; what are they, what kind of cycles they occur in, what
magnetic fields are associated with them and what their temperature is.
Describe at least two types of solar activity other than sunspots.
Describe how the interior structure of the Sun is determined. What
observations are made, what information is contained in the observations
and how is the information used to determine the structure?