AST 1002 COMPREHENSIVE ANSWERS AND
QUESTIONS SET A+
✔✔One star in a binary will almost always become a red giant before the other because
- ✔✔small differences in main-sequence masses yield large differences in main-
sequence lifetimes
✔✔A nova is the result of which explosive situation? - ✔✔mass transfer onto a white
dwarf
✔✔What occurs if a white dwarf exceeds the Chandrasekhar limit - ✔✔a type 1a
supernovae explosion
✔✔If you measure the average brightness and pulsation period of a Cepheid variable
star, you can also determine its - ✔✔distance
✔✔The CNO cycle in high-mass main-sequence stars burns ________ to ________in
their cores - ✔✔hydrogen; helium
✔✔When the core of a massive star collapses, a neutron star forms because: -
✔✔protons and electrons combine to form neutrons
✔✔Which of the following is true about the instability strip on the H-R diagram? -
✔✔stars show variability in their brightness
evolved stars pulsate
location of RR Lyrae and Cepheids
✔✔Why does the luminosity of a high-mass star remain nearly constant as the star
burns heavy elements in its core, even though it is producing millions of times more
energy per second than it did on the main sequence? - ✔✔most of the energy is carried
out of the star by escaping neutrinos
, ✔✔Essentially all the elements heavier than iron in our galaxy were formed - ✔✔by
supernovae
✔✔A neutron star contains a mass of up to 3 M☉ in a sphere with a diameter
approximately the size of - ✔✔a city
✔✔What is the radius of the event horizon of a 10 solar mass black hole? - ✔✔30km
✔✔Hawking radiation is emitted by a black hole when: - ✔✔a virtual pair of particles is
created from the vacuum of space.
✔✔Gravitational lensing occurs when ________ distorts the fabric of spacetime -
✔✔any massive object
✔✔we classify all galaxies as - ✔✔how they appear in the sky
✔✔The disks of spiral galaxies appear blue because: - ✔✔spiral galaxies are still
undergoing star formation
✔✔Light is increasingly redshifted near a black hole because: - ✔✔time is moving
increasingly slower in the observer's frame of reference.
✔✔Active star formation does not occur in elliptical galaxies because they: - ✔✔contain
little molecular hydrogen
✔✔What does the Hubble tuning fork illustrate? - ✔✔a classification theme
✔✔Why does the central bulge of a spiral galaxy appear red when compared to the
color of the spiral arms? - ✔✔There is no star formation there, and the star population is
dominated by old, long-lived, low-mass red stars.
✔✔Besides shape, what characteristic clearly separates elliptical galaxies from spiral
galaxies? - ✔✔color
✔✔What is observed to happen to the velocities of stars that reside at greater distances
from the center of the galaxy? - ✔✔they essentially stay the same
✔✔Why is 21-cm radiation a good spiral arm tracer? - ✔✔Emitted by neutral hydrogen,
it traces the location of concentrations of gas.
✔✔Why do rotation curves of galaxies imply that dark matter exists? - ✔✔The velocity
of stars stays somewhat constant at distances beyond the visible edges of galaxies,
implying that more matter than what we observe in stars and gas must be there.
QUESTIONS SET A+
✔✔One star in a binary will almost always become a red giant before the other because
- ✔✔small differences in main-sequence masses yield large differences in main-
sequence lifetimes
✔✔A nova is the result of which explosive situation? - ✔✔mass transfer onto a white
dwarf
✔✔What occurs if a white dwarf exceeds the Chandrasekhar limit - ✔✔a type 1a
supernovae explosion
✔✔If you measure the average brightness and pulsation period of a Cepheid variable
star, you can also determine its - ✔✔distance
✔✔The CNO cycle in high-mass main-sequence stars burns ________ to ________in
their cores - ✔✔hydrogen; helium
✔✔When the core of a massive star collapses, a neutron star forms because: -
✔✔protons and electrons combine to form neutrons
✔✔Which of the following is true about the instability strip on the H-R diagram? -
✔✔stars show variability in their brightness
evolved stars pulsate
location of RR Lyrae and Cepheids
✔✔Why does the luminosity of a high-mass star remain nearly constant as the star
burns heavy elements in its core, even though it is producing millions of times more
energy per second than it did on the main sequence? - ✔✔most of the energy is carried
out of the star by escaping neutrinos
, ✔✔Essentially all the elements heavier than iron in our galaxy were formed - ✔✔by
supernovae
✔✔A neutron star contains a mass of up to 3 M☉ in a sphere with a diameter
approximately the size of - ✔✔a city
✔✔What is the radius of the event horizon of a 10 solar mass black hole? - ✔✔30km
✔✔Hawking radiation is emitted by a black hole when: - ✔✔a virtual pair of particles is
created from the vacuum of space.
✔✔Gravitational lensing occurs when ________ distorts the fabric of spacetime -
✔✔any massive object
✔✔we classify all galaxies as - ✔✔how they appear in the sky
✔✔The disks of spiral galaxies appear blue because: - ✔✔spiral galaxies are still
undergoing star formation
✔✔Light is increasingly redshifted near a black hole because: - ✔✔time is moving
increasingly slower in the observer's frame of reference.
✔✔Active star formation does not occur in elliptical galaxies because they: - ✔✔contain
little molecular hydrogen
✔✔What does the Hubble tuning fork illustrate? - ✔✔a classification theme
✔✔Why does the central bulge of a spiral galaxy appear red when compared to the
color of the spiral arms? - ✔✔There is no star formation there, and the star population is
dominated by old, long-lived, low-mass red stars.
✔✔Besides shape, what characteristic clearly separates elliptical galaxies from spiral
galaxies? - ✔✔color
✔✔What is observed to happen to the velocities of stars that reside at greater distances
from the center of the galaxy? - ✔✔they essentially stay the same
✔✔Why is 21-cm radiation a good spiral arm tracer? - ✔✔Emitted by neutral hydrogen,
it traces the location of concentrations of gas.
✔✔Why do rotation curves of galaxies imply that dark matter exists? - ✔✔The velocity
of stars stays somewhat constant at distances beyond the visible edges of galaxies,
implying that more matter than what we observe in stars and gas must be there.
