The main sequence has a limit at the lower end because
there is a minimum
temperature for hydrogen fusion.
There is a mass-luminosity relation because
stars support their weight
by making energy.
As a star like the sun exhausts hydrogen in its core,
the outer layers of the star
become cooler
and more luminous.
Helium fusion is called the triple alpha process
because
the helium
nucleus is known as an alpha particle.
A star will experience a helium flash if
its core is degenerate
when helium ignites.
In degenerate matter
pressure does not depend
on temperature.
Giant and supergiant stars are rare because
the giant and
supergiant stage is very short.
Variables of a certain type are called Cepheid variable because
the first one
discovered was in the constellation of Cepheus.
When the Cepheid variable RU Camelopardalis stopped pulsating, astronomers
speculated that it was
evolving out of the
instability strip.
A young star cluster will have _______________ than an older star cluster.
a bluer turn-off point
Open clusters tend to be _______________ than globular
clusters.
younger and
contain fewer stars
Star cluster are important to our study of stars
because
they give us a method to
test the our theories and models of stellar evolution.
The triple alpha process
occurs during
helium flash.
A star in the instability strip pulsates because
density and
opacity of the helium ionization zone changes with time.
The lowest mass object that can initiate thermonuclear
fusion of hydrogen has a mass of about
0.08 M
Which of the following nuclear fuels does a one solar
mass star use over the course of its entire evolution?
hydrogen and
helium
Which of the following nuclear fuels does a 0.2 solar
mass star use over the course of its entire evolution?
hydrogen
Helium flash occurs
because
degenerate electrons in the core do not allow the core to expand as it heats
up.
A Cepheid variable with a mass of 10 M
_______________ than a Cepheid of 3 M.
has a longer
period
RR Lyrae variables
are less
luminous than Cepheid variables.
The changing period of a Cepheid variable tells us
that the
star is
evolving.
It is assumed that stars in a star cluster
all have the
same age & all have the same chemical composition.
If the stars at the turnoff point of a cluster have a mass
of 3 M,
what is the age of the cluster?
6.4
108 years
What is the lifetime of a 10 M star on the main sequence?
3.2107 years
The lowest-mass stars cannot become giants because
they cannot
heat their centers hot enough.
A planetary nebula is
the expelled
outer envelope of a medium mass star.
The Chandrasekhar limit tells us that
not all stars
will end up as white dwarfs.
In A.D. 1054, Chinese astronomers observed the
appearance of a new star, whose location is now occupied by
a supernova
remnant.
Massive stars cannot generate energy through iron
fusion because
iron is the
most tightly bound of all nuclei.
The theory that the collapse of a massive star's iron
core produces neutrinos was supported by
the detection
of neutrinos from the supernova of 1987.
A Type I supernova is believed to occur when
a white dwarf exceeds the
Chandrasekhar limit.
Synchrotron radiation is produced by
high-velocity electrons
moving through a magnetic field.
A nova is almost always associated with
a white dwarf
in a close binary system.
The Algol paradox is explained by considering
mass transfer
between the two stars in a binary system.
Stars with masses between 0.4 M and 4 M
undergo thermonuclear
fusion of hydrogen and helium, but never get hot enough to ignite carbon.
A type-II supernova
is characterized by a
spectrum that shows hydrogen lines & occurs when the iron core of a massive
star collapses.
The Helix and Egg nebulae are
planetary nebulae.
Synchrotron radiation is produced
in supernova remnants.
When material expanding away from a star in a binary system
reaches the Roche surface
the material is no longer
gravitationally bound to the star.
As material leaves an expanding star and begins to fall into a
white dwarf
an accretion disk will form
around the white dwarf.
A white dwarf is composed of
carbon and oxygen nuclei
and degenerate electrons.
A planetary nebula
produces an emission
spectrum.
If the theory that novae occur in close binary systems
is correct, then novae should
repeat after
some interval.
A typical planetary nebula will be visible for about
50,000 years.
We know that the central object in a planetary nebula
has a surface temperature of at least _______________ K because the nebula
contains large amounts of ionized hydrogen.
25,000 K
As a white dwarf cools its radius does not change
because
pressure does not depend
on temperature for a white dwarf because the electrons are degenerate.
A supernova remnant is expanding in radius at the rate
of 0.5 seconds of arc per year. Doppler shifts show that the velocity of
expansion is 5700 km/sec. How far away is the supernova remnant?
2400 pc
Suppose that a planetary nebula is 0.5 parsecs in
diameter and expanding at 20 km/s. How old is it? (Hint: 1 pc = 3.11013
km.)
12,000 years
The _____________________ are places in the orbital plan of a
binary star system where a bit of matter can reach stability. The one located
directly between the two stars is the point where the Roche lobes meet.
|
Lagrangian points |
The Crab nebula is
A supernova remnant
Stars less than 0.4 solar masses
are totally convective
Which main-sequence star
would be the least luminous?
G5
If you moved 4
times as far from a star, the star would appear?
16 times fainter.
In the proton-proton chain
energy is produced in the
form of gamma rays and the velocity of the created nuclei.
Emission
nebulae are also called _______________ because they are composed of
ionized
hydrogen.
HII regions.
Observations
from the Compton Gamma Ray Observatory showed that gamma ray bursters were
located throughout the sky. This told us that
the bursts were not
produced among stars in our galaxy.
To determine the period of a visual binary, we must measure
|
|
position |
An eclipsing binary will
|
|
always be a spectroscopic binary. |
If a luminous object were moved to one-half the original distance,
it would appear
|
|
four times brighter. |
||||
|
|
|||||
If a star were 100 parsecs away, what would be the parallax?
|
|
0.01 arc seconds |
If you moved 4 times as far from a star, the star would appear
|
|
16 times fainter. |
||||
Why are white dwarfs and red dwarfs, which are very common, NOT
visible to the unaided eye?
|
|
They are too faint. |
||||
|
|
|||||
|
|
|||||
A parsec is roughly equal to
|
|
3.26 light-years. |
|
|
Opacity is
|
|
a measure of the ease with which photons can pass through a gas. |
||||
|
|
||||
In the protonproton chain,
|
|
energy is produced in the form of gamma rays and the velocity of
the created nuclei. |
||||
Emission nebulae are also called _______________________ because
they are composed of ionized hydrogen.
|
|
HII regions |
The main sequence has a limit at the lower end because
|
|
there is a minimum temperature for hydrogen fusion. |
The carbon-nitrogen-oxygen cycle
|
|
combines four hydrogen nuclei to form one helium nucleus, which
produces energy. |
The nuclear reactions in a star’s core remain under control so
long as
|
|
pressure depends on temperature. |
The lowest mass object that can initiate thermonuclear fusion of
hydrogen has a mass of about
|
|
0.08 solar mass. |
Low-mass stars
|
|
consume their fuel slowly and live long lives |
__________________________ are starlike objects that contain less
than 0.08 solar masses an will never raise their core temperatures to the point
that the proton–proton chain can begin. They fall in a gap between the low-mass
M dwarf stars and the massive planets.
Question options:
|
|
Brown dwarfs |
||
Planetary nebulae are
|
|
the expanding shells of a dying star. |
||||
A type I supernova is believed to occur when
|
|
a white dwarf exceeds the Chandrasekhar limit. |
||||
The lowest-mass stars CANNOT become giants because
|
|
they cannot heat their centers hot enough. |
||||
Stars in a star cluster
|
|
all have the same age. |
||||
|
|
all have the same chemical composition. |
||||
|
|
all have the same luminosity. |
||||
|
|
all of the above |
||||
|
|
a and b above |
||||
As a star exhausts hydrogen in its core, it
|
|
becomes cooler and more luminous. |
||||
Stars less than 0.4 solar masses
|
|
are totally convective. |
||||
A nova is almost always associated with
|
|
a white dwarf in a close binary system. |
||||
A planetary nebula is
|
|
the expelled outer envelope of a medium-mass star. |
||||
|
|||||
Star clusters are important to our study of stars because
|
|
they give us a method to test our theories and models of stellar
evolution. |
An
isolated black hole in space would be difficult to detect because
|
|
very
little matter would be falling into it |
||||
|
|||||
Cygnus
X-1 and LMC X-3 are black holes if the masses of the unseen companions
are
|
|
more
than 5 solar masses |
||||
|
|||||
Neutron
stars are expected to spin rapidly because
|
|
they
conserved angular momentum when they collapsed |
||||
|
|||||
Observations
from the Compton Gamma Ray Observatory showed that gamma-ray bursters were
located throughout the sky. This told us that
|
|
the
bursts were not produced among stars in our galaxy |
||||
|
|||||
Although neutron stars are very hot, they are not easy to locate because
|
|
they
have small surface areas |
||||
|
|||||
Pulsars
are believed to slow down because
|
|
they
are converting energy of rotation into radiation |
||||
|
|||||
How
fast do gravity waves travel?
|
|
The
speed of light |
||||
|
|||||
Pulsars
cannot be spinning white dwarfs because
|
|
a
white dwarf spinning that fast would fly apart |
||||
|
|||||
The
density of a ________________ is greater than the density of a
_________________.
|
|
pulsar;
white drawf |
1.
Observations from the Compton Gamma Ray Observatory showed that gammaray
bursters were
located throughout the sky. This told us that
* a. the
bursts were not produced among stars in our galaxy.
2. _________________ occurs when light travels out of a gravitational field,
loses
energy and
its wavelength grows longer.
* c. A
gravitational redshift
3. A
_________ has a radius of about 10 km and is supported by the pressure
associated
with
degenerate neutrons.
* b. neutron
star
4. The
slowing of clocks in strongly curved space time is known as
* b. time
dilation.
5. Pulsars are believed to slow down because
* a. they are
converting energy of rotation into radiation.
6. Cygnus X-1
and LMC X-3 are black holes if the masses of the unseen companions
are
* b. more
than 5 solar masses.
7. The search for black holes involves searching for
* b. X-ray
binaries where the compact companion has a mass in excess of 3 M
8.
Fraud in science is rare because it is difficult to commit. Why is it difficult
to commit
fraud in
science?
a. Science
requires that experimental and theoretical findings be reproducible.
b. All
scientists are bound by a code of ethics preventing them from publishing
fraudulent
work.
c. Scientific
results are reviewed by other scientists before they are published.
d. Scientific
journals only allow certain highly trusted individuals to publish their
work.
* e. a and c
above
9. The first
pulsar was discovered by ____________ in November of 1967.
* a. Jocelyn
Bell
10. As a star exhausts hydrogen in its core, it
* b. becomes
cooler and more luminous.
11. In degenerate matter
* c. pressure
does not depend on temperature.
12. Giant and supergiant stars are rare because
* c. the
giant and supergiant stage is very short.
13. In star clusters, the _____________ stars are giant stars fusing helium in
their cores
and then in
their shells.
* e.
horizontal branch
14. The _____________________ are places in the orbital plan of a binary star
system
where a bit
of matter can reach stability. The one located directly between the two
stars is the
point where the Roche lobes meet.
* c.
Lagrangian points
15. What is
the approximate age of the star
cluster in
the diagram on the right?
* c 10
billion years
16. The
triple alpha process
* e. occurs
during helium flash
17. A
planetary nebula is
* a. the
expelled outer envelope of a medium mass star.
18. The Chandrasekhar limit tells us that
* d. not all
stars will end up as white dwarfs.
19. The Algol
paradox is explained by considering
* e. mass
transfer between the two stars in a binary system.
20. Stars
with masses between 0.4 M and 4 M
* a. undergo
thermonuclear fusion of hydrogen and helium, but never get hot
enough to
ignite carbon.
21. Emission nebulae are also called _______________ because they are composed
of
ionized
hydrogen.
* b. HII
regions
22. The average star spends _________ of its lifetime on the main sequence.
* e. 90%
23. The
free-fall contraction of a molecular cloud
* a. can be
initiated by shock waves from supernovae.
24. There is a mass-luminosity relation because
* c. stars
support their weight by making energy.
26. _________ require(s) that a young hot star (T 25,000 K) be
relatively nearby.
* a. Emission
nebulae
27. Giant stars are
I. more
luminous than the sun.
II. larger in
diameter than the sun.
III. Cooler
than B stars.
IV. located
above the main sequence stars in the H-R diagram.
a. I & II
b. II &
IV
c. I, II,
& IV
d. II, III,
& IV
* e. I, II,
III, & IV
28. Circini
is an O 8.5 V star. Based on this information which of the following are
true?
I. Circini has a
surface temperature less than the sun.
II. Circini has a
diameter that is greater than that of the sun.
III. Circini is
more luminous than the sun.
IV. Circini is
located near the upper left hand corner in the HR diagram.
a. I & II
b. II &
IV
* c. II, III,
& IV
29. In a binary system, the more massive star
* c. is
nearest the center of mass.
30. Spectroscopic binaries are difficult to analyze because
* b. we can't
see the shape of the orbit.
34. If we can solve the orbital motion of an eclipsing binary, we can find
a. the masses
of the stars & b. the diameters of the stars.
35. Which of
the following best obey the mass-luminosity relation?
* a. main
sequence stars
36. A spectroscopic binary shows periodic variations in its
* a. radial
velocity.
37. Stars on the main sequence with the greatest mass
* b. are
spectral type O stars.
