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Chapter 13, 14, and 15 Test
Richardson
65
Astronomy
Undergraduate 1
04/22/2010

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Term
What is a white dwarf?
Definition
Exposed core of a dead star.
Term
small size + star mass = ?
Definition
High gravity
Term
how is the white dwarf star balanced against gravity?
Definition
by electron degeneracy pressure
Term
why do white dwarfs shine brightly in the X-ray region?
Definition
because they are so hot
Term
One solar mass star produces a white dwarf made of what?
Definition
carbon
Term
About how big is a white dwarf star?
Definition
about the size of the earth
Term
A teaspoon of material from a white dwarf is equal to..
Definition
severl tons of weight on Earth
Term
The heavier a white dwarf is, the ________ it becomes.
Definition
SMALLER
Term
No white dwarf can have more mass than how many solar masses?
Definition
1.4 solar masses
Term
What is the Chandrasekhar Limit?
Definition
It says that no white dwarf can have more mass than 1.4 solar masses.
Term
how fast would degenerate electrons have to travel to counter gravity?
Definition
faster than the speed of light.
Term
Can white dwarfs have fusion by themselves?
Definition
no
Term
What system allows for a white dwarf to gain mass by stripping gas from its neighbor?
Definition
a binary system
Term
According to the Conservation of Angular Momentum, material falling in to a white dwarf ____ gains speed as it gets closer
Definition
GAINS
Term
Expain the process of a Novae
Definition
-Hydrogen from neighbour falls to surface
-As it falls it gets hot, and when it hits the surface it gets compressed
-Thin hot layer of hydrogen builds up on the surface of the white dwarf
-when the temperature reaches 10 million K
-BOOM!
Term
Explain the process of a Supernovae
Definition
-A white dwarf can gain mass
-it it's mass approaches 1.4 solar masses, carbon fusion starts
-Fusion takes place everywhere at the same time
-Instantaneous fusion leads to the white dwarf exploding
Term
What are Neutron Stars?
Definition
the remnant of a massive star
Term
The iron core of a Neutron star becomes all________.
Definition
neutrons
Term
Neutron stars are _____ massive than the sun.
Definition
more
Term
How is the neutron star balanced against gravity?
Definition
by neutron degeneracy pressure
Term
Where are pulsars found?
Definition
at the center of nebulae

... therefore pulsars are neutron stars
Term
Explain the process of the pulsar
Definition
-as the iron core collapses, it has to spin faster
-Collapse pulls magnetic field lines closer together -> very strong magnetic poles
-the poles emit radiation
-If the poles are not aligned with the spin axis, you get a lighthouse effect.
Term
What do pulsars use to power themselves?
Definition
rotational energy
Term
as a pulsar emits power, the rate at which it spins at _________
Definition
decreases
Term
slowly, over time, the pulses from a pulsar take _______ and _______ to occur
Definition
longer and longer
Term
Can neutron stars pull material from it's companion?
Definition
yes, just as white dwarfs do
Term
how is an accretion disk formed?
Definition
pulling material from a companion star
Term
stronger ________ allows materials to heat up further
Definition
gravity
Term
pulsars from X-ray binaries _______ speed, unlike usual pulsars.
Definition
increase
Term
describe the process of x-ray bursters
Definition
-the in-falling Hydrogen creates a layer on the star surface
-steady Hydrogen fusion takes place.
-At the base of the layer, Helium builds up and it begins to burn in bursts
Term
What does the term "black hole" refer?
Definition
refers to the fact that even the speed of light is not fast enough for an object to escape from it
Term
the term "hole" refers to what?
Definition
a hole in space-time
Term
What is the event horizon?
Definition
the boundary point of being able to escape a black hole and never being able to escape it
Term
what is the Schwarzschild Radius?
Definition
it describes the size of the event horizon

-it depends only on the mass of the object forming the black hole
Term
A black hole formed by a star of 1 solar mass has a radius of 3 kilometers.. so a star of 10 solar masses would form a black hole with a radius of __ kilometers
Definition
30
Term
Once the star has collapsed past the event horizon, it is a ______ _____
Definition
black hole
Term
The ______ outside of a black hole is still the same as for the star
Definition
gravity
Term
Singularity
Definition
refers to a point
Term
in a black hole, what is the singularity?
Definition
where all the star mass goes
Term
What two things happen as a clock with blue numbers is pushed into a black hole?
Definition
As the clock is falling:

1. the numbers turn redder the further the clock falls

2. time ticks more slowly the further it falls
Term
What are the tidal effects of a clock that is pushed into a black hole?
Definition
-the further the clock falls, the more it becomes stratched
-it is stretched due to the increasing change in gravity the closer to the event horizon it gets
Term
Describe the clocks experience as it reaches the event horizon
Definition
-from the clocks point of view, nothing about it slows down. It still ticks the same rate as it had outside the hole

-however, upon reaching the event horizon, the clock will feel itself smoothly pass through it

-the observer watching the clock would require a radio telescope to see the numbers and would NEVER see the clock enter the event horizon
Term
How can we find black holes?
Definition
Most compelling evidence is in binaries, such as Cygnus X-1 where a visible 8 solar mass object is orbiting an invisible 10 solar mass object that emits x-rays.
Term
What is a Gamma Ray Burst?
Definition
When a star collapses into a black hole.
Term
What is a Hypernova?
Definition
When a star with 40-100 solar masses collapses into a black hole which lasts longer than 2 seconds.
Term
What is a short duration gamma burst?
Definition
When a neutron star collapses into a black hole, or when two neutron stars collide.
Term
What are orbital patterns in a galaxy?
Definition
1) Old halo stars orbit in any direction.
2) Disk stars, old and young, orbit within the disk.
3) Old bulge stars orbit very fast around the center.
Term
How did galaxies form?
Definition
Protogalactic clouds from the Big Bang condensed down and squished dust into a spinning disk where stars began to form and recycle in the disk.
Term
How much mass does our galaxy have and what does it argue?
Definition
Our galaxy has a mass of 2 x 10^41kg, and since it doesn't look like there is that much in our galaxy it is possible evidence of dark matter.
Term
When light is reflected by dust it appears to be ____?
Definition
Blue
Term
When light is reflected by dust it appears to be ____?
Definition
Blue
Term
When light passes through dust it appears to be ___?
Definition
Red
Term
What are thought to be at the center of every galaxy?
Definition
Supermassive Black Holes
Term
What proof is there that black holes are at the center of galaxies?
Definition
Orbital patterns of stars near the center of the galaxy suggest that they orbit an object 3-4 solar masses yet that mass is squished into about the size of our solar system.
Term
What are the three main shapes of galaxies?
Definition
Spiral, Elliptical/Spheroidal, and Irregular
Term
How many stars are there in Dwarf Galaxies?
Definition
100 million
Term
How many stars are there in Giant Galaxies?
Definition
1 trillion
Term
Galaxies are generally part of a _____?
Definition
Group
Term
How can we make a guide for the evolution of galaxies?
Definition
By looking at galaxies that are very far away from us because the light we see is old and thus we can make a guide by comparing old galaxies to new ones and tracking their development.
Term
Galaxies have formed in large groups because in the early Universe they had to overcome _______ _________
Definition
Universal Expansion
Term
Why are galaxies different?
Definition
Because of protogalactic spin and protogalactic density.
Term
At the center of large clusters of galaxies are huge central dominant galaxies. How did they get to be so big?
Definition
They consumed their neighbors which makes a stronge case that elliptical galaxy evolution involves galaxy collisions.
Term
What are Starbursts?
Definition
When galaxies collide there is huge pressure and very high temperature which leads to the production of stars en masse. Starburst galaxies can produce up to if not more than 100 new stars per year.
Term
Quasars are radio sources that have strong unknown spectral lines and are thought to be...?
Definition
Active centers of galaxies traveling at up to 17% the speed of light.
Term
What is one theory about the formation of Jets from incoming material into Supermassive Black Holes?
Definition
One theory is that the Magnetic Fields in the Black Hole sends energy flying out of the Black Hole along Magnetic Field Lines.
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