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Quiz Review: Star Formation
Star Formation
1. What is accretion? What force starts this process? What force finishes this
process?
Objects colliding forming a larger object. Electromagnetic force starts this process
until the object is massive enough for gravity to take over.
2. What triggers star formation in these nebula and where do they come from?
Supernovas….they come from the most massive stars exploding
3. Describe the balance that exists during a stars main sequence. Draw a diagram
of this.
Gravity = Fusion
4. What is fusion? Where does the energy come from? Draw a diagram of this.
Fusion creates huge amounts of energy… 1 atom of Helium is lighter
than 2 atoms of hydrogen because when the collision occurs a small
amount of matter is converted into a huge amount of
energy…E=mc2
5. What has a higher fusion temperature, helium or hydrogen?
Helium…the heavier the element the higher the fusion temperature
6. The main sequence of a star begins with the fusion of what?
Hydrogen…fusion of hydrogen begins when core reaches 15 million degrees
7. Describe the life cycle of a low mass star like the sun from birth to death. Make
sure you understand what is happening in between each stage.
See star life cycle hand out…
8. Describe the path of a high mass star from life to death, include both ways they
can end depending on mass. Make sure you understand what is happening
between each stage.
See star life cycle hand out…
Star Death
9. Do more massive or less massive stars live shorter lives? Why?
More massive stars burn through their fuel faster just like bigger cars use more fuel
10. Describe the red giant stage of a low mass star.
When all of the hydrogen is fused in the core the star expands to fuse any
remaining hydrogen in the outer layers…this is why the star gets so big…it turns red
because as it expands the outer layers cool down.
Once all of the hydrogen in the outer layers is burned fusion stops and gravity
causes the star to collapse. As the star collapses the core heats up and the fusion
of helium begins. The star expands again as it fuses helium. Carbon builds up in
the core as helium fuses. Once all of the helium is fused the star collapses again.
The star is not massive enough to heat the core to the temperatures required for
carbon to fuse.
The outer layers are then poofed off as a planetary nebula…leaving the carbon core
of the star behind.
11. Our sun life cycle ends when helium is fused to make carbon and oxygen. Why
does it end here?
Not massive enough for the stars collapse to ignite helium.
12. What happens to stars like our sun when it dies?
Outer layers are poofed off as a planetary nebula (peaceful event)…carbon core is
left behind this is called a white dwarf
13. What is left over after the planetary nebula?
White dwarf (carbon core)
14. What do we think happens to a white dwarf star? Why is this hard to predict?
1. Since our universe is only about 13.5 billion years old a white dwarf
is yet to have completely burned out
2. If a white dwarf has cooled it will not emit light and we cannot see
it (black dwarf)
15. What is a brown dwarf?
Failed star…1/10 solar masses…Jupiter thought to be one
16. Describe the red supergiant stage of high mass stars. What elements are
created during this stage?
When all of the hydrogen is fused in the core the star expands to fuse any
remaining hydrogen in the outer layers…this is why the star gets so big…it turns red
because as it expands the outer layers cool down.
Once all of the hydrogen in the outer layers is burned fusion stops and gravity
causes the star to collapse. As the star collapses the core heats up and the fusion
of helium begins. The star expands again as it fuses helium. Carbon builds up in
the core as helium fuses. Once all of the helium is fused the star collapses again.
These stars are massive enough to heat up enough to fuse carbon into even
heavier elements. The most massive stars will collapse and heat up fusing all
elements up to iron (26 protons).
17. What element cannot be fused inside the core of a star?
Iron!
18. What is a supernova? List 2 reasons why supernovas are important.
When fusion is no longer going on in a star’s core it collapses colliding with the
core. This is one of the most energetic events in the universe. More energy is
emitted during the supernova than the star emitted its entire life.
Important because: this is when all elements heavier than iron are formed and these
elements are necessary for life to exist on Earth.
19. What are the 2 types of supernovas? Explain each.
Type Ia: 2 stars in a binary system…white dwarf pulls material off of red giant until it
ignites and goes supernova
Type II: high mass star cant fuse iron and outer layers collide with core
20.What do stars between 4-10 solar masses become?
Neutron star
21. Explain how a neutron star is formed.
After the supernova 20% of the star still remains and this mass still has a huge
gravitational force. This gravitational force crushes atoms remaining in core.
Protons and electrons are fused together by gravity making neutrons.
22. What is a pulsar?
Neutron stars spin extremely fast (1000 times per second). Any remaining electrons
not fused with protons are excited by the stars rotation and interact with the neutron
stars magnetic field. This interaction releases huge amounts of energy from the
neutron stars N and S pole and they are seen as pulsars.
They are important because this is how we see neutron stars from Earth.
23. What do stars with a solar mass bigger than 10 become?
Black Hole
24. How are black holes formed?
Core is so massive that its gravity crushes it to a small enough size (Schwartzchild
radius)
25. What is the event horizon?
Point of no return…gravity is so strong nothing can escape
26.How can black holes be used as a means to travel between universes?
They are so massive they can bend the fabric of spacetime so much that
they may be able to stretch to other parallel universes.
27. What is a quasar? What is a radio jet?
Quasar is energy given off by material being pulled toward a black hole at
high speeds. Matter collides and heats up due to friction. This is seen as a
quasar.
Radio jets are energy emitted out of black hole.
Solar System Formation
28. Name all of the main objects in our solar system.
The Sun, 8 planets, hundreds of known moons and thousands of asteroids, meteors
and comets
29.Where is the majority of the mass located in our solar system?
The Sun contains about 99.9% of the material in the solar system
30.What is an AU?
1 AU = Distance from the Sun to the Earth…about 93 million miles
31. What is the name of the theory that explains our solar system’s formation?
Nebular Theory
32. Explain how this theory describes our solar systems formation.
 States that everything in the solar system formed from the nebula
that the Sun originated from
o This nebula was rich in heavier elements from earlier stars
going supernova
o It is these elements that allowed life to form on Earth
 Before a star reaches main sequence it’s in the protostar stage
o During this stage a star has a disk of dust and gas rotating
around it
o This disk is the source of the planets
o The rotation and turbulence in the dust and gas around the
protostar caused it to sort itself out into concentric rings
33. What is some evidence for this theory?
1) All planets revolve around the Sun in the same direction and on roughly the
same plane
2) All planets except Venus and Neptune rotate in the same direction as the Sun
3) All moons rotate in the same direction as the planet they orbit
4) The planets appear to have a regular spacing, each planet is twice as far as
from the Sun as the planet in front of it
5) The Sun is thought to be 4.6 billion years old, all rocks that have been dated
are roughly the same age
o Oldest rocks ever dated (in Canada) are about 4.1 billion years old
6) Meteors that have crashed into Earth have similar chemical compositions as
rocks on Earth
7) In stars the densest material falls to the center, if the solar system formed
during the Sun’s formation the heaviest elements should be closest to the
center of the solar system
o The terrestrial or inner planets are made of heavy elements such as
metals and silicates (rock). The outer planets are much less dense and
have much thicker atmospheres of gas
34. Where did the heavier elements that are present in our solar system come
from?
Massive stars and element heavier than iron came from supernovas
35. What are the terrestrial planets?
Inner rocky planets…thin atmospheres few moons
36.
Why are these planets rocky and have few moons?
Gas was too hot early in solar systems formation. The gas molecules were the
material for atmospheres and moons but they were moving too fast for the inner
planets gravitational force to hold onto.
They are rocky because metals and silicates are denser than gas molecules. The
densest material was closest to the Sun so the inner planets are made up of these
materials.
37. What are the Jovian planets and why do they have many moons?
The outer planets…they have more moons and thicker atmospheres because the gas
was cool enough to form these things as it moved further out into the solar system.
38. What is the Kuiper belt?
Asteroid belt that contains Pluto
39.
Why isn’t Pluto a planet anymore?
We discovered many other objects similar in size to Pluto so we had to re-classify it
as a dwarf planet.
40.What is the Oort cloud and what comes from here?
Huge ring of ice and dust outside Kuiper Belt…furthest region of our solar
system…comets come from here
41. Difference between comets, asteroids, and meteors.
Comet- chunk of ice and rock orbiting Sun
Asteroid- chunk of rock and metal orbiting Sun
Meteoroid- asteroid that is 10 m or less in size…becomes a meteor when it enters
Earth’s atmosphere…meteorite if it reaches ground
42. What is the Rare Earth Theory? What is the goldilocks zone?
Says that conditions for Earth to form are rare but are possible given the number of
solar systems in our own galaxy. Goldilocks zone is distance a planet must be from
its star in order for liquid water to be present on the surface of that planet.