PHY 108 - Study Questions Set 3
1.
What process provides the power for the Sun?
A.
fusion of helium into carbon
B.
fission of uranium to form lead
C.
emission of neutrinos
D.
fusion of hydrogen into helium
2.
What is a positron?
A.
the nucleus of a helium atom
B.
a positive electron
C.
the nucleus of a hydrogen atom
D.
a chargeless, massless particle
3.
The phrase "hydrostatic equilibrium" in the Sun refers to
A.
the balance of gas pressure outward and magnetic forces inward.
B.
the creation of one helium nucleus for the "destruction" of every four hydrogen nuclei.
C.
the balance of gas pressure inward and heat outward.
D.
the balance of gravity inward and gas pressure outward.
4.
From the center outward, the order of the layers or parts of the Sun is
A.
radiative zone, convection zone, corona, chromosphere, photosphere.
B.
radiative zone, convection zone, chromosphere, photosphere, corona.
C.
corona, chromosphere, convection zone, photosphere, radiative zone.
D.
radiative zone, convection zone, photosphere, chromosphere, corona.
5.
What is the Sun's photosphere?
A.
the middle layer of the Sun's atmosphere
B.
the lowest layer of the Sun's atmosphere
C.
the envelope of convective mass motion in the outer interior of the Sun
D.
the upper layer of the Sun's atmosphere
6.
The granulation pattern seen on the surface of the Sun results from
A.
heating of the photosphere by solar flares.
B.
the differential rotation of the Sun.
C.
strong magnetic fields cooling the gas in certain regions.
D.
convection of gas in the region under the photosphere.
7.
What is the name of the layer of the Sun's atmosphere that appears as a pinkish ring just outside the visible disk of the Sun during a total solar eclipse?
A.
the chromosphere
B.
the convective zone
C.
the photosphere
D.
the corona
8.
The temperature of the corona of the Sun
A.
is about the same as that of the photosphere, 5800 K.
B.
is about twice as hot as the photosphere, 12,000 K.
C.
is very cool, because it is farthest from the heat source.
D.
is very hot—about 10
6
K.
9.
What is the source of the X rays emitted by the solar corona?
A.
radioactivity in the coronal gases
B.
X rays from the solar photosphere scattered from ions in the corona
C.
the high temperature gas of the corona
D.
high-energy charged particles spiraling along the coronal magnetic fields
10.
What is the solar wind?
A.
the storm of waves and vortices on the Sun's surface generated by a solar flare
B.
the constant flux of photons from the Sun's visible surface
C.
the circulation of gases between the equator and the poles of the Sun
D.
the Sun's outer atmosphere streaming out into space
11.
The solar wind appears to originate mainly from which regions of the Sun?
A.
sunspots
B.
all over the surface, with no preferred location
C.
granulation cells
D.
coronal holes
12.
What is the lifetime of a typical sunspot?
A.
from a few hours to a few months
B.
from a few years to a few decades
C.
11 years
D.
Here today, gone tomorrow!
13.
What is the structure of a typical large sunspot?
A.
an irregular dark area of uniform darkness
B.
a dark center surrounded by a less dark area
C.
a roughly circular, dark region with a lighter central area
D.
usually round and of uniform darkness
14.
The major feature that distinguishes a sunspot from other regions on the Sun is
A.
that it is much brighter than its surroundings.
B.
its very powerful magnetic field.
C.
faster rotation around the Sun's axis than neighboring regions.
D.
the coronal hole that exists above it.
15.
Suppose that, at night, the brightness of a light bulb is measured from a certain distance and then the light bulb is moved to a distance twice as far away. How bright will the light appear compared to the earlier measurement?
A.
1/16 as bright
B.
1/2 as bright
C.
1/8 as bright
D.
1/4 as bright
16.
The luminosity of a star is
A.
the energy output of 1 m
2
of its surface space at all wavelengths.
B.
its brightness when measured from Earth.
C.
its total energy output emitted at all wavelengths into all space.
D.
its brightness when measured from a distance of 10 parsecs, or 32.6 light-years.
17.
The relative brightnesses of stars as we see them in our sky are represented on star charts in terms of their
A.
surface temperatures.
B.
absolute magnitudes.
C.
apparent magnitudes.
D.
luminosities.
18.
Measurements of the brightness of a distant star through the three appropriate filters indicate that the star is brightest in U, less bright in B, and faintest in V. What conclusion can be drawn from this information, assuming no absorption of light between the star and Earth?
A.
This information is insufficient to allow a conclusion to be drawn about star surface temperature.
B.
The star has an intermediate temperature, close to the Sun.
C.
The star has a very low surface temperature.
D.
The star has a very high surface temperature.
19.
The Hertzsprung-Russell diagram is a plot of
A.
apparent brightness vs. intrinsic brightness or luminosity of a group of stars.
B.
luminosity vs. period of variation for variable stars.
C.
apparent brightness vs. distance for stars near the Sun.
D.
intrinsic brightness or luminosity vs. temperature of a group of stars.
20.
Compared to a star in the middle of the diagram, a star in the lower left part of the Hertzsprung-Russell diagram is
A.
brighter.
B.
larger.
C.
cooler.
D.
smaller.
21.
Observations of binary stars have helped astronomers to determine which important scientific parameter?
A.
the universal gravitational constant
B.
stellar masses
C.
the speed of light in deep space
D.
the sizes of stars
22.
Where do we find the most massive stars on the main sequence in a Hertzsprung-Russell diagram?
A.
upper left
B.
They all have approximately the same mass, because this is what defines the main sequence.
C.
lower right
D.
center, with lower mass stars on either side
23.
The predominant color of an emission nebula is
A.
red, from the hydrogen Balmer H
a
line.
B.
blue, from scattering of light from hot stars by dust particles.
C.
green-yellow, from the 530.3 nm-emission line of ionized iron, equivalent to that from the hot solar corona.
D.
a continuum of all colors, the combined light from all the stars in the nebula.
24.
The most likely places in which stars and planetary systems are forming in the universe are
A.
the rarified outer space between galaxies.
B.
regions of hot gas in the spiral arms of galaxies.
C.
gas and dust nebulae.
D.
the centers of galaxies.
25.
Protostars, when they FIRST form from the interstellar medium, are usually
A.
detected easily because their light ionizes the surrounding interstellar gas, forming H II regions.
B.
very bright in ultraviolet light due to numerous flares (like solar flares but hotter and brighter).
C.
hidden from sight by dust clouds that emit infrared radiation.
D.
detected by emission lines in their visible spectra, emitted by gas being blown off their surfaces into space.
26.
What is the most abundant element in the universe?
A.
helium
B.
hydrogen
C.
carbon
D.
oxygen
27.
What condition is considered sufficient for an interstellar cloud to collapse and form a star or stars (i.e., if this condition holds then the cloud has to collapse)?
A.
The cloud must be alone in space, far from the gravitational influence of stars or other interstellar clouds.
B.
The cloud must be cooler than 100 K.
C.
Gravity must be strong enough to reach all parts of the cloud.
D.
Gravity must dominate gas pressure inside the cloud.
28.
The source of a protostar's heat is
A.
gravitational energy, released as the star contracts.
B.
gravitational energy, released as the protostar expands.
C.
nuclear reactions converting helium to carbon and oxygen in its core.
D.
nuclear reactions converting hydrogen into helium in its core.
29.
What prevents a star from having a mass greater than about 200 solar masses?
A.
No interstellar clouds are found that contain more than 200 solar masses.
B.
A star of larger mass would collapse under its own gravity, and the whole star would become a black hole.
C.
Gas pressure becomes so high as a consequence of high temperatures, that the excess mass is pushed back into space.
D.
The core of a larger-mass star would evolve rapidly and explode before the overall star finished contracting as a protostar.
30.
What event occurs at the end of the protostar stage of a star's life?
A.
Nuclear reactions begin in its core, converting hydrogen into helium, generating energy and increasing internal pressure.
B.
It explodes, forming a supernova remnant.
C.
It begins a long period of contraction, in which gravitational energy is converted into heat.
D.
Gas is spun off from its equator, forming planets.
31.
Why does the core of the Sun contain more helium and less hydrogen than the surface material of the Sun?
A.
Thermonuclear reactions have converted much of the original hydrogen in the core into helium.
B.
The hydrogen has been lifted out of the core by the Sun's magnetic field.
C.
Helium is heavier than hydrogen and has sunk toward the center in a process of chemical differentiation.
D.
Helium condensed more easily, so the core became helium-rich when the Sun was first forming. Vast quantities of hydrogen were added only after the core became massive enough.
32.
When a star leaves the main sequence and expands toward the red giant region, what is happening inside the star?
A.
Hydrogen burning is taking place in a spherical shell just outside the core; the core itself is almost pure helium.
B.
Hydrogen burning is taking place in a spherical shell just outside the core; the core has not yet started thermonuclear reactions and is still mostly hydrogen.
C.
Helium burning is taking place in a spherical shell just outside the core; the core itself is almost pure carbon and oxygen.
D.
Helium is being converted into carbon and oxygen in the core.
33.
Under what conditions does electron degeneracy occur?
A.
when electrons become crowded too closely together
B.
when thermonuclear reactions release more electrons than protons
C.
when electrons and positrons annihilate, releasing energy
D.
when ultraviolet light from hot, young O and B stars ionizes the interstellar medium
34.
What unusual process is involved in the helium flash?
A.
An increase in temperature causes an increase in the nuclear reaction rate but has no effect on pressure.
B.
An increase in temperature causes an increase in the pressure with no increase in the nuclear reaction rate.
C.
An increase in the pressure causes a decrease in the temperature and the nuclear reaction rate.
D.
An increase in the nuclear reaction rate causes an increase in the temperature and the pressure.
35.
In describing a star, what does the adjective "metal-poor" mean?
A.
The star has a low abundance of all elements in its spectrum.
B.
The star has a low abundance of all elements heavier than hydrogen in its spectrum.
C.
The star may or may not have a low abundance of carbon in its spectrum, but it is definitely weak in iron.
D.
The star has a low abundance of all elements heavier than hydrogen and helium in its spectrum.
36.
In a semidetached binary star system,
A.
the stars share the same outer atmosphere, but the cores of the two stars do not touch.
B.
one star fills its Roche lobe, while the other does not.
C.
one star orbits the center of mass, while the other moves freely through space.
D.
both stars fill their Roche lobes.
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