ASTRO (Science) EXAM 3 FINAL EXAM
QUESTIONS CORRECTLY ANSWERED.
What is a protostar?
Before fusion of protons to produce helium dense core contracts to become a true
star and called protostar
Briefly describe evolution of a star with a mass like that of the sun, from the
main- sequence phase of its evolution until it becomes a white dwarf
When the sun becomes more stable and compact the sun has an electron
degenerate core that cant contract further
Interior structure of the white dwarf star before final collapse (outer to inner)
hydrogen envelope, hydrogen shell fusion, helium core, helium fusion, carbon-
oxygen core
Briefly describe the evolution of a massive star up to stage after at which it
becomes a supernova.
Neutron star is 20 km in diameter and rotating neutron star having magnetism starts
pulsating electromagnetic beam, then becomes a pulsar
Interior structure of the super nova star before its final collapse (outer to inner)
hydrogen envelope, hydrogen & helium fusion, helium fusion, carbon & oxygen
fusion, magnesium & neon, oxygen fusion, silicon sulfur fusion, iron ash
Supernovae Type Ia
Ignited by lots of material dumped on degenerate white dwarfs
Supernovae Type II
Massive stars, when core collapses
If all the stars in a cluster have nearly the same age, why are clusters useful in
studying evolutionary effects
,More massive stars evolve most rapidly, most luminous blue stars on main sequence.
Stars with lowest masses to the right of main sequence stars of lower masses evolve
away from main sequence
Population I stars
Typically younger, found in disk, contain heavier elements
Population II Stars
Few heavy elements, found in halo and global clusters
Spiral Galaxies
Galaxies with old and young stars, interstellar matter, star masses range 10^9-
10^12 Msun
Elliptical Galaxies
Elongated system, entirely old stars, little interstellar matter, star masses usually
10^6 Msun
Hubbles Law
Spectral lines of distant galaxies redshifted recession velocities proportion to
distance from us
Hubbles Constant
Rate of recession, approx. 22 kilometers per second per million light years
Explain Einsteins equivalence principle
No possibility anyone or any experiment in sealed environment can tell the
difference between free fall and no gravity
Three experiments/observations that verify Einsteins general theory of relativity
Time Dilation: Time slows in curved space-time
Stronger gravity means more slowly time moves
Theory of relativity agrees with Newtons law of gravity in weak gravitational fields
What does it mean to say that the universe is expanding? What is expanding?
,The universe is expanding means the universe undergoes a change in scale with
time. Space stretches and distances grow larger by same factor everywhere at a
given time
The interstellar medium is composed of mainly
mostly gas and some dust
Large molecular clouds will form into protostars because of
gravitational contraction
What is the approximate upper limit of a brown dwarf's size (mass)?
less than 0.08 solar masses
The fusion of helium into carbon will take a temperature of at least
100 million degrees Kelvin
The Chandrasekhar limit defines
maximum mass of a white dwarf
As a white dwarf ages, its position on a standard H-R diagram will move
downward and to the left
Binary systems with pairs of stars orbiting each other are
common, and important for some types of stellar evolution
What positive effect have supernovae had on the development of life on Earth?
Chemical elements necessary for life can only be formed in the supernovae
A neutron star is created when a
collapsing stellar core exceeds the Chandrasekhar limit
A black hole is
an object so dense that light cannot escape its surface
The event horizon of a black hole is the point where
the escape velocity equals the speed of light
Astronauts approaching a black hole would observe that
, they become stretched thin their heads and feet are pulled apart by gravitational
tides
The Sun orbits the center of the galaxy about once every
225, 000, 000 years
Dark matter is
an unknown type of mass that does not emit or absorb photons
The mass of visible matter in a galaxy can be estimated by measuring its
luminosity. When this is compared with the measured mass of the galaxy,
astronomers find that
the measured mass is about ten times the estimated mass, due to the effects of dark
matter
The expansion of the Universe
was slower in the early Universe when galaxies were close to each other, and has
accelerated thereafter
T/F Stars are born from the interstellar medium, and aging or dying stars return
gas and dust back into the interstellar medium
true
T/F One of the major star forming regions in space is the Orion Nebula
true
T/F A white dwarf is an neutron degenerate object, while a neutron star is a
electron degenerate object
false
T/F Every star spends most of its total lifetime on the main sequence
true
T/F The event horizon is located at the Schwarzschild radius
true
T/F The presence of the black hole in the center of the galaxy has been
determined by observing the motion of stars orbiting it
QUESTIONS CORRECTLY ANSWERED.
What is a protostar?
Before fusion of protons to produce helium dense core contracts to become a true
star and called protostar
Briefly describe evolution of a star with a mass like that of the sun, from the
main- sequence phase of its evolution until it becomes a white dwarf
When the sun becomes more stable and compact the sun has an electron
degenerate core that cant contract further
Interior structure of the white dwarf star before final collapse (outer to inner)
hydrogen envelope, hydrogen shell fusion, helium core, helium fusion, carbon-
oxygen core
Briefly describe the evolution of a massive star up to stage after at which it
becomes a supernova.
Neutron star is 20 km in diameter and rotating neutron star having magnetism starts
pulsating electromagnetic beam, then becomes a pulsar
Interior structure of the super nova star before its final collapse (outer to inner)
hydrogen envelope, hydrogen & helium fusion, helium fusion, carbon & oxygen
fusion, magnesium & neon, oxygen fusion, silicon sulfur fusion, iron ash
Supernovae Type Ia
Ignited by lots of material dumped on degenerate white dwarfs
Supernovae Type II
Massive stars, when core collapses
If all the stars in a cluster have nearly the same age, why are clusters useful in
studying evolutionary effects
,More massive stars evolve most rapidly, most luminous blue stars on main sequence.
Stars with lowest masses to the right of main sequence stars of lower masses evolve
away from main sequence
Population I stars
Typically younger, found in disk, contain heavier elements
Population II Stars
Few heavy elements, found in halo and global clusters
Spiral Galaxies
Galaxies with old and young stars, interstellar matter, star masses range 10^9-
10^12 Msun
Elliptical Galaxies
Elongated system, entirely old stars, little interstellar matter, star masses usually
10^6 Msun
Hubbles Law
Spectral lines of distant galaxies redshifted recession velocities proportion to
distance from us
Hubbles Constant
Rate of recession, approx. 22 kilometers per second per million light years
Explain Einsteins equivalence principle
No possibility anyone or any experiment in sealed environment can tell the
difference between free fall and no gravity
Three experiments/observations that verify Einsteins general theory of relativity
Time Dilation: Time slows in curved space-time
Stronger gravity means more slowly time moves
Theory of relativity agrees with Newtons law of gravity in weak gravitational fields
What does it mean to say that the universe is expanding? What is expanding?
,The universe is expanding means the universe undergoes a change in scale with
time. Space stretches and distances grow larger by same factor everywhere at a
given time
The interstellar medium is composed of mainly
mostly gas and some dust
Large molecular clouds will form into protostars because of
gravitational contraction
What is the approximate upper limit of a brown dwarf's size (mass)?
less than 0.08 solar masses
The fusion of helium into carbon will take a temperature of at least
100 million degrees Kelvin
The Chandrasekhar limit defines
maximum mass of a white dwarf
As a white dwarf ages, its position on a standard H-R diagram will move
downward and to the left
Binary systems with pairs of stars orbiting each other are
common, and important for some types of stellar evolution
What positive effect have supernovae had on the development of life on Earth?
Chemical elements necessary for life can only be formed in the supernovae
A neutron star is created when a
collapsing stellar core exceeds the Chandrasekhar limit
A black hole is
an object so dense that light cannot escape its surface
The event horizon of a black hole is the point where
the escape velocity equals the speed of light
Astronauts approaching a black hole would observe that
, they become stretched thin their heads and feet are pulled apart by gravitational
tides
The Sun orbits the center of the galaxy about once every
225, 000, 000 years
Dark matter is
an unknown type of mass that does not emit or absorb photons
The mass of visible matter in a galaxy can be estimated by measuring its
luminosity. When this is compared with the measured mass of the galaxy,
astronomers find that
the measured mass is about ten times the estimated mass, due to the effects of dark
matter
The expansion of the Universe
was slower in the early Universe when galaxies were close to each other, and has
accelerated thereafter
T/F Stars are born from the interstellar medium, and aging or dying stars return
gas and dust back into the interstellar medium
true
T/F One of the major star forming regions in space is the Orion Nebula
true
T/F A white dwarf is an neutron degenerate object, while a neutron star is a
electron degenerate object
false
T/F Every star spends most of its total lifetime on the main sequence
true
T/F The event horizon is located at the Schwarzschild radius
true
T/F The presence of the black hole in the center of the galaxy has been
determined by observing the motion of stars orbiting it
