Download Star Questions 2008 - Fort Thomas Independent Schools

Astronomy
Chapters 10-13
Star Questions: Evolution of Stars
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How do stars form?
What does it mean for a star to have a life cycle?
Explain what it means for a star to be on the main sequence.
Which two pressures act upon any star on the main sequence?
Why a star remains roughly the same diameter when on the
main sequence.
Explain the following relationships:
a. Surface temperature and color
b. luminosity and mass
c. absolute and apparent brightness
What is the H-R Diagram?
Describe the death of these two stars, one with 2 solar masses
and one with 10 solar masses.
What is a supernova and what is its significance?
Describe the difference between a Type I and Type II
supernova?
What will happen to our Sun when it dies?
Which is more luminous, a low-mass or a high-mass star? Explain.
What is a neutron star?
What is a black hole?
What is the Chandrasekhar Limit?
1. How do stars form?
See the Nebular Theory, chapter 5. Stars
form from the dust and gases of a cold
nebula. Compression event causes the
matter to move and rotate, gravitational
attraction causes the matter to clump,
continued gravitational collapse increases
the mass and temperature until a protostar
develops. If greater than 0.08 solar masses,
the temperature rises at the center of the
protostar to 10 million K and initiates
thermonuclear fusion of hydrogen into
helium.
2. What does it mean for a star to have a
life cycle?
The star proceeds through stages of birth,
life on the main sequence and death.
3. Explain what it means for a star to be on
the main sequence.
A star on the main sequence is fusing
hydrogen into helium at its core.
4. Which two pressures act upon any star
on the main sequence?
Gravitational pressure (inward) and thermal
pressure due to thermonuclear fusion
(outward)
5. Why a star remains roughly the same
diameter when on the main sequence.
There is a balance of force between the
gravitational pressure and thermal pressure.
6. Explain the following relationships:
a. Surface temperature and color
The color changes with the temperature of
the star. Red stars are cooler than blue
stars.
b. luminosity and mass
Luminosity and mass are directly
proportional. As mass increases, so does
luminosity.
c. absolute and apparent brightness
Absolute brightness or magnitude is the true
brightness of the star as seen from 10
parsecs from the Earth, the apparent
brightness or magnitude is the brightness of
the star as seen from the Earth.
7. What is the H-R Diagram?
A graph showing the relationship of star
absolute magnitude, luminosity, color,
spectral class and temperature. The main
sequence stars are aligned at the center of
the graph. Illustrates life cycle of stars.
8. Describe the death of these two stars,
one with 2 solar masses and one with 10
solar masses.
Two solar masses: red giant to white dwarf,
quiet loss of gases produce a nebula.
10 solar masses: red supergiant to
supernova to either a neutron star or black
hole.
9. What is a supernova and what is its
significance?
A core collapse of a supermassive star or a
star that has a core mass that exceeds 1.4
solar masses that produces an extreme
explosion and fuses all heavy elements
observed in the universe.
10. Describe the difference between a Type
I and Type II supernova?
Type I supernovae develop as the star
accumulates more matter than it had when
it was on the main sequence, causing the
core to grow to a size greater than 1.4 solar
masses.
Type II supernovae occur when a
supermassive star (> 8 solar masses) goes
through core collapse and rebound,
exploding violently.
11. What will happen to our Sun when it
dies?
It will expand (red giant), fuse helium at it
core, slow release its gases and become a
white dwarf (hot carbon core). Death will
begin in 5 billion years.
12. Which is more luminous, a low-mass or a
high-mass star? Explain.
High mass stars are larger, so they emit more
electromagnetic radiation or energy.
13. What is a neutron star?
An extremely dense core of a large mass
star (> 8 solar masses) that resulted from a
supernova
14. What is a black hole?
The result from a supermassive star that goes
supernova, a black hole represents the total
and utter unstoppable collapse of matter,
gravity exceeds any degenerate pressure
that could stop the collapse.
15. What is the Chandrasekhar Limit?
The limit of mass in the core of a star that will
not allow the star to go supernova. 1.4 solar
masses