Download 1) The following questions refer to the HR diagram

1) The following questions refer to the H-R diagram below that shows the life track of a 1-solar-mass star, with various
stages labelled with Roman numerals.
Which stage lasts the longest?
A) viii B) i
C) iv
D) iii
E) vi
2) On a Hertzsprung-Russell diagram, where would we find white dwarfs?
A) upper left
B) lower right C) lower left
D) upper right
3) A star of spectral type O lives approximately how long on the main sequence?
A) 10,000 years
B) 1 million years
C) 1,000 years
D) 1 billion years
E) 100 million years
4) The spectral sequence sorts stars according to
A) radius.
B) mass.
C) luminosity.
D) surface temperature.
E) core temperature.
5) On a Hertzsprung-Russell diagram, where on the main sequence would we find stars that have the
greatest mass?
A) upper right
B) lower left
C) lower right
D) upper left
6) The following questions refer to the sketch below of an H-R diagram for a star cluster.
Based on its main-sequence turnoff point, the age of this cluster is
A) about 10 billion years.
B) less than 1 billion years.
C) more than 15 billion years.
D) about 2 billion years.
E) about 1 billion years.
7) In an H-R Diagram, stars with the smallest radius are found in the _______ of the diagram.
a. center
b. upper left corner
c. upper right corner
d. lower left corner
e. lower right corner
8) Use the following HR diagram to answer the next question.
Which star in the diagram above is most like the sun?
a. Alnilam
b. Antares
c. Arcturus
d. HR 5337
e. Sirius B
9) Stars on the main sequence with the greatest mass
a. are spectral type M stars.
b. are spectral type O stars.
c. are located at the bottom of the main sequence in the HR diagram.
d. have masses very similar to the sun.
e. both b and c
10) Which star in the table above has the greatest luminosity?
a. 65 Tau
b. HR 4621
c. α Pic
d. 58 Ori
e. HR 2491
11) Which star in the table above has the greatest surface temperature?
a. 65 Tau
b. HR 4621
c. Pic
d. 58 Ori
e. HR 2491
12). A 2 solar mass star on the main sequence would have a luminosity of approximately ________ solar
luminosities.
a. 2
b. 4
c. 11
d. 0.5
e. 0.25
13) According to the H-R diagram in Figure 16-1A, the areas labeled C and D would be classified as:
a. white dwarfs.
b. red giants.
c. red and blue supergiants.
d. the main sequence.
14) According to the H-R diagram in Figure 16-1A, the areas labeled B and E would be classified as:
a. red giants.
b. the main sequence.
c. red and blue supergiants
d. white dwarfs.
15) As a group, stars known as main sequence stars on an H-R diagram are best described as being:
a. hotter.
b. brighter.
c. stable.
d. larger.
16) Which is the same for all stars along a horizontal line on an HR diagram?
(a) temperature
(b) diameter
(c) mass
(d) luminosity
17) A Main Sequence M star has a radius of about 7 x 10 7 m and a surface temperature of about 3000 K. An M
supergiant star has the same surface temperature, but has a radius 1000 times bigger. How much more luminous is the
M supergiant than the Main Sequence M star?




a) they have the same luminosity
b) the M supergiant is 1000 times more luminous
c) the M supergiant is a million times more luminous
d) you can't tell without knowing the distances to the two stars
18) What is the ultimate fate of an isolated pulsar?
A) As gravity overwhelms the neutron degeneracy pressure, it will explode as a supernova.
B) It will spin ever faster, becoming a millisecond pulsar.
C) The neutron degeneracy pressure will eventually overwhelm gravity and the pulsar will slowly
evaporate.
D) As gravity overwhelms the neutron degeneracy pressure, it will become a white dwarf.
E) It will slow down, the magnetic field will weaken, and it will become invisible
19) What happens when the gravity of a massive star is able to overcome neutron degeneracy pressure?
A) The star explodes violently, leaving nothing behind.
B) The core contracts and becomes a black hole.
C) The core contracts and becomes a white dwarf.
D) The core contracts and becomes a ball of neutrons.
E) Gravity is not able to overcome neutron degeneracy pressure.
20) What is the ultimate fate of an isolated white dwarf?
A) As gravity overwhelms the electron degeneracy pressure, it will explode as a supernova.
B) The electron degeneracy pressure will eventually overwhelm gravity and the white dwarf will slowly
evaporate.
C) As gravity overwhelms the electron degeneracy pressure, it will become a neutron star.
D) As gravity overwhelms the electron degeneracy pressure, it will explode as a nova.
E) It will cool down and become a cold black dwarf.
21) White dwarfs are so called because
A) it amplifies the contrast with red giants.
B) they are both very hot and very small.
C) they are supported by electron degeneracy pressure.
D) they are the end-products of small, low-mass stars.
E) they are the opposite of black holes.
22) What happens to the surface temperature and luminosity when a protostar radiatively contracts?
A) Its surface temperature remains the same and its luminosity decreases.
B) Its surface temperature and luminosity remain the same.
C) Its surface temperature decreases and its luminosity increases.
D) Its surface temperature and luminosity decrease.
E) Its surface temperature and luminosity increase.
23) What causes the radio pulses of a pulsar?
A) A black hole near the star absorbs energy and re-emits it as radio waves.
B) The star vibrates.
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) As the star spins, beams of radio radiation sweep through space. If one of the beams crosses the earth,
we observe a pulse.
24) Which of the following statements about stages of nuclear burning (i.e., first-stage hydrogen burning, second-stage
helium burning, etc.) in a massive star is not true?
A) Each successive stage creates an element with a higher atomic weight.
B) As each stage ends, the core shrinks further.
C) Each successive stage of fusion requires higher temperatures than the previous stages.
D) Each successive stage lasts for approximately the same amount of time.
25) Degeneracy pressure is the source of the pressure that stops the crush of gravity in all the following except
A) a neutron star.
B) a brown dwarf.
C) the central core of the Sun after hydrogen fusion ceases but before helium fusion begins.
D) a very massive main-sequence star.
E) a white dwarf.
26) Why did the solar nebula heat up as it collapsed?
a) Nuclear reactions inside the protosun produced energy that heated the nebula.
b) Light from other nearby stars heated the nebula.
c) The solar nebula was heated when it collided with other clouds of interstellar material.
d) As the nebula shrank, its gravitational potential energy was converted into the random kinetic energy of the
nebula’s molecules.
e) Collisions among planetesimals generated heat.
27) In a star, hydrostatic equilibrium requires a balance between __________ and __________.
a) temperature; luminosity
b) rate of energy generation; luminosity
c) pressure; gravity
d) radiation; convection
e) radius; mass
28) Near the end of its life, the Sun will likely lose about one-half of its mass __________.
a) as it ejects its envelope to form a planetary nebula
b) as it ejects its envelope in a supernova explosion
c) as it ejects its envelope to form a dusty molecular cloud
d) when powerful magnetic fields disrupt the Sun
e) as it generates a new family of planets from material in its envelope