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Quiz Review: Star Formation
Parallax
1. What is parallax?
The apparent shift in a stars location. This apparent shift is caused by the Earth’s
rotation around the sun.
2. Find the parallax of the star in the image below. The scale given in 1 arc
second.
a. Remember parallax = 1/d
0.8 parsecs
b. How many light years away is this star?
0.8 x 3.26 = 2.6 light years
c. How many miles away is this star?
2.6 l.y. x 5.9 x 1012 = 1.538 x 1013
3. From horizon to horizon it is 180 degrees. The apparent movement of stars is
so small we have to use units smaller than this. Explain how each degree is
broken down to the smallest increment. What is the point directly above you
called?
Each degree is broken up into 60 arc minutes. Each minute is broken up
into 60 arc seconds…basically each degree (size of your thumb) contains
3600 arc seconds. Point above you is called zenith.
Star Formation
4. 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.
5. What triggers star formation in nebula?
Supernovas….they come from the most massive stars exploding. There are other
things that can trigger star formation such as galactic collisions, and spiral arms of
galaxies colliding.
6. Describe the balance that exists during a stars main sequence. Draw a diagram
of this.
Force of gravity (derived from star’s mass) is in equilibrium with the fusion pushing
out from the core.
7. What are the 2 types of fusion? Explain why each is important.
Proton-Proton chain: responsible for elements up to oxygen (8 protons)
CNO (carbon, nitrogen, oxygen) Cycle: responsible for elements up to iron (26
protons)
8. What has a higher fusion temperature, helium or hydrogen?
Helium…the more protons an element has the higher the fusion temperature.
9. The main sequence of a star begins with the fusion of what?
Hydrogen (1 proton)
10. 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 flow chart of star life cycle.
11. 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 flow chart of star life cycle.
Star Death
12. 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
13. 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
14. 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
15. 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
16. What is left over after the planetary nebula?
White dwarf (carbon core)
17. What do we think happens to a white dwarf star? (2 theories)
Since our universe is only about 13.5 billion years old a white dwarf
is yet to have completely burned out
If a white dwarf has cooled it will not emit light and we cannot see
it (black dwarf)
18. What is a brown dwarf?
Failed star…1/10 solar masses…Jupiter thought to be one
19. 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).
20.What element cannot be fused inside the core of the most massive stars?
Iron!
21. 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.
22. 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
23. What do stars between 5-10 solar masses become?
Neutron star
24. 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.
25. What is a pulsar and magnetar?
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.
Magnetars are neutron stars with an extreme magnetic field.
26.What do stars with a solar mass bigger than 10 become?
Black Hole
27. How do black holes form?
Core is so massive that its gravity crushes it to a small enough size (Schwartzchild
radius)
28. What is the event horizon?
Point of no return…gravity is so strong nothing can escape
29.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.
30.How do we see black holes?
Gravitational lensing
31. What is the Schwarzschild radius?
The radius something must be condensed into in order to become a black hole. If
Earth were crushed to the size of a peanut it would be a black hole.
32. What is a quasar? What is a radio jet? Blasar?
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.
Blasars are when the stream of energy is facing the Earth. It is like staring
down the barrel of the gun.