A White Dwarf cannot be more massive than 1.4 solar masses
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Chandrasekhar limit
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Nova
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The sudden fusion of hydrogen to helium at the surface of a white dwarf
Can last for a few weeks
Can shine as bright as 100,000 suns
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Nova or Supernova?
Nova
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H to He fusion of a layer of accreted matter, white dwarf left intact
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Nova or Supernova?
Supernova
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Complete explosion of white dwarf, nothing left behind
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Massive star supernova:
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Iron core of massive star reaches white dwarf limit and collapses into a neutron star, causing an explosion
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White dwarf supernova:
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Carbon fusion suddenly begins as white dwarf in close binary system reaches white dwarf limit, causing a total explosion
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Why does a Type Ia supernova have no hydrogen lines while a Type II does
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A Type Ia Supernova (white Dwarf) doesn't have hydrogen so they couldn't have hydrogen lines whereas Type II (Massive Star) has excess hydrogen.
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Neutron Star
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Not a star -- corpse
Essential a giant atomic nucleus, made almost entirely of neutrons held together by gravity.
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Pulsar
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Spinning neutron star
DOES NOT PULSE
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Matter falling on surface of neutron star continuously produces energy released as...
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Low-level x-rays
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Neutron star Limit
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Neutrons in the same place cannot be in the same state
Neutron degeneracy pressure can no longer support a neutron star against gravity if its mass exceeds about 3MSun
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Which of these objects has the smallest radius?
a 1.2MSun white dwarf
a 0.6MSun white dwarf
Jupiter
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A 1.2MSun white dwarf
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If we see a nova, we know that we are observing
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A white dwarf in a binary system
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What would happen to a neutron star with an accretion disk orbiting in a direction opposite to the neutron star's spin?
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It would slow down
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Make sense, yes or no
The best way to search for black holes is to look for small black circles in the sky
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No
Cannot distinguish between objects that do not emit or reflect light and their black background using direct observations
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Which of these objects has the largest radius?
1.2MSun white dwarf
a 1.5MSun neutron star
a 3.0MSun black hole
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1.2MSun white dwarf
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What would happen if the Sun suddenly became a black hole without changing its mass?
The black hole would quickly suck in the Earth.
Earth would gradually spiral into the black hole.
Earth's orbit would not change
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Earth's orbit would not change
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Viewed from a distance, how would a flashing red light appear as it fell into a black hole?
It would appear to flash more quickly.
Its flashes would appear bluer.
Its flashes would shift to the infrared part of the spectrum.
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Its flashes would shift to the infrared part of the spectrum
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The radius of a white dwarf is determined by a balance between the inward force of gravity and the outward push of ...
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Electron Degeneracy Pressure
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A _______ occurs when hydrogen fusion ignites on the surface of a white dwarf in a binary system.
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Nova
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A __________ occurs when fusion creates iron in the core of a star.
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Massive Star Supernova
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Rotating magnetic field causes electric field that rips charged particles from star's surface and accelerates them
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Rotating magnetic field causes electric field that rips charged particles from star's surface and accelerates them
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Lighthouse Model
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Rotating neutron star with different magnetic and rotation axes
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Accretion disks emit...
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X-rays
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X-ray bursters
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An object that emits irregularly spaced bursts of x-rays
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Neutron degeneracy pressure can no longer support a neutron star against gravity if its mass exceeds about...
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3MSun
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Gravitational Lensing
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Exaggerated bending of the path of light passing near the Sun
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If M remaining is < 1.4 MSun
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White Dwarf
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1.4 MSun < If Mass remaining < 3 MSun
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Neutron Star
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If Mass remaining is < 3MSun
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Black Hole
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What is a black hole?
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Since gravity is so great in a black hole, nothing can withstand it
Eventually it will have a radius of zero
Infinite density
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Surface of a Black Hole
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The radius at which the escape velocity equals the speed of light
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What is the "Event Horizon"
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Spherical surface of a black hole
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Schwarzschild radius
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The radius of the event horizon
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Event horizon definition
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The boundary that marks the "point of no return" for photons between a black hole and the outside universe
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All mass has a _____________________ _________.
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Schwarzschild radius
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A 1 MSun has a Schwarzschild radius of about
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3 km
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Earth would become a black hole if its Schwarzschild radius became less than
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1 cm
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Size of a black hole is determined by the size of the
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Event Horizon
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Size of the event horizon is determined by the mass of ....
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The black hole
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More mass means _________ event horizon
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Larger
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Black Holes have only 3 Properties
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Mass
Electric Charge
Angular Momentum
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As you approach the black hole light will be...
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Gravitationally Redshifted
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True or False
If a black hole is part of a binary system an accretion disk can form around it
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True
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While black holes emit nothing, the accretion disk will emit
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Beams of x-rays
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Two Types of Gamma Ray bursts
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One type is from a Supernova that produces a black hole
Other type is from a neutron star colliding with another neutron star or black hole
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