chapter 14
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81 Terms
what is a white dwarf
a small, dense remnant of a low-mass star
what can happen to a white dwarf in a close binary system
it can explode as a supernova
what prevents a white dwarf from collapsing under its own gravity
degeneracy pressure
what is a neutron star
a remnant core left after a supernova explosion, composed of mostly neutrons
how were neutron stars discovered
by detecting pulsars, which are rapidly rotating neutron stars emitting beams of radiation
what can happen to a neutron star in a close binary system
it can accrete matter and emit x-rays
what is a black hole
a region of space where gravity is so strong that not even light can escape
what would it be like to visit a black hole
you would experience time dilation and extreme tidal forces
do black holes really exist
yes, they have been confirmed through various observations such as gravitational waves and x-ray emissions from accretion disks
what causes gamma-ray bursts
the collision and merger of neutron stars or the collapse of massive stars
what happens when neutron stars merge
they form either a more massive neutron star or collapse into a black hole while emitting gravitational waves and gamma-ray bursts
what happens when black holes merge
they form a single, more massive black hole while emitting gravitational waves
what is a white dwarf
the exposed core of a star that has died and shed its outer layers
which type of pressure supports a white dwarf against the crush of gravity
electron degeneracy pressure
what happens to the temperature of a white dwarf over time
it slowly cools
what is the primary composition of a white dwarf left behind by a sun-like star
carbon
how does the size of more massive white dwarfs compare to less massive ones
more massive white dwarfs are smaller in size
what would be the approximate weight of a teaspoon of a white dwarf matter on earth
several tons
what is the maximum mass that a white dwarf can have, known as the chandrasekhar limit
1.4 times the mass of the sun
why can’t a white dwarf have a mass greater than 1.4 times the mass of the sun
electron speeds would reach the speed of light, which is not possible
what observational evidence supports the theoretical limit on the mass of white dwarfs
all observed white dwarfs have masses below 1.4 times the mass of the sun
what can happen to a white dwarf in a close binary system with a main-sequence or giant star companion
it can gradually gain mass through an accretion disk
how does gas behave in an accretion disk around a white dwarf
gas in the inner region orbits faster than gas in the outer region
what new energy source can accretion provide to an otherwise “dead” white dwarf
gravitational potential energy converted into thermal and radiative energy
what causes hydrogen fusion to ignite on the surface of a white dwarf, leading to a nova
the temperature at the bottom of an accreted hydrogen layer reaches about 10 million k
how does accretion affect successive novae on a particular system
accretion resumes after each nova explosion, allowing for repeated novae
what happens when carbon fusion ignites almost instantly throughout an entire white dwarf
the white dwarf explodes completely in what is called a white dwarf
how can two closely orbiting white dwarfs lead to one reaching the chandrasekhar limit
they emit gravitational waves, causing them to spiral inward and merge
how do astronomers distinguish between different types of supernovae
by studying thier light spectra and luminosity patterns
what primarily supports a neutron star against the crush of gravity
neutron degeneracy pressure
how does the density of neutron star material compare to that of ordinary matter
it is so dense that a paper clip made of it would outweigh mount everest
what would happen if a small piece of neutron star material appeared on earth
it would pass through the earth due to its immense weight and density
how does the mass and size of a typical neutron star compare to that of the sun
more massive and much smaller than the sun
what is the escape velocity at the surface of a neutron
about half the speed of light
who discovered the first observational evidence for neutron stars and when
jocelyn bell burnell in 1967
what phenomenon did jocelyn bell burnell discover that led to identifying neutron stars
rapidly pulsing radio waves at precise intervals
why are pulsars considered cosmic lighthouses
they emit beams of radiation that sweep past earth as they rotate, creating pulses we can detect
why do pulsars gradually slow down over time
their magnetic fields generate electromagnetic radiation that carries away energy and angular momentum
what rule can be derived about pulsars and neutron stars based on their characteristics
all pulsars are neutron stars, but not all neutron stars are pulsars
what type of radiation do accretion disks around neutron stars primarily emit
x-ray radiation
why do x-ray binaries with accreting neutron stars often have rapidly pulsating emissions
the accreting matter adds angular momentum, causing the neutron star’s rotation rate to increase, leading to rapid pulsations in x-rays emitted by the accretion disk
what is the defining characteristic of a black hole
its escape velocity exceeds the speed of light
according to einstein’s general theory of relativity, what causes gravity
the curvature of spacetime
why is it impossible for light to escape from a black hole
the gravitational pull inside a black hole is too strong for light to escape
what is the event horizon of a black hole
the boundary at which the escape velocity equals the speed of light
what determines the schwarzchild radius of a black hole
its mass
how does the size of the schwarzchild radius change with increasing mass
its mass increases
what happens to matter inside a black hole according to current theories
it gets crushed into an infinitely tiny and dense point called a singularity
which two theories make different predictions about the nature of singularities in black holes
general relativity and quantum physics
why can’t we observe what happens inside a black hole’s event horizon
because it emits no radiation or light detectable by telescopes
what is a gravitational redshift
a shift in light frequency due to strong gravitational fields affecting time and space
what would happen to an object as it approaches the event horizon from an outside observer’s perspective
it would appear to slow down and eventually freeze in time as it reaches the event horizon due to gravitational redshift effects
why would tidal forces near a small black hole be lethal for humans
because they would stretch and compress objects with extreme force differences over short distances
how does supernova contribute towards formation process leading up to creation involving possible stellar remnants like neutron stars and black holes
by causing collapse under own gravity leading up to formation involving neutron star or possibly even further collapsing into forming black hole if conditions exceed certain limits
what evidence supports existence regarding supermassive black holes residing within centers involving many galaxies including milky way
observations regarding extreme events occurring within universe along with indirect influences exerted upon surrounding celestial bodies suggesting presence regarding such massive objects influencing their behavior significantly over time periods involved during study conducted so far till date
why do astronomers believe some x-ray binaries contain black holes instead of neutron stars
because they emit stronger x-rays compared against those emitted by neutron stars indicating presence involving more massive object involved within system studied so far till date
what was the initial purpose of the satellites that first detected gamma-ray bursts
to detect nuclear bomb tests
why do scientists believe that gamma-ray bursts channel their energy into narrow beams
because their luminosity is too high to be explained otherwise
what is the primary evidence linking gamma-ray bursts to exploding stars
observations of gamma-ray bursts coinciding with supernova explosions in other wavelengths of light
what type of supernova is likely responsible for the most extreme gamma-ray bursts
a supernova forming a black hole
what percentage of gamma-ray bursts are different in character and last only a few seconds
about 30%
what happens when 2 neutron stars merge
they emit gravitational waves and produce a blend of rare elements, including gold and platinum
how was it confirmed that neutron star mergers can produce short gamma-ray bursts
by detecting gravitational waves followed by a burst of gamma rays from the fermi satellite in 2017
where did the first confirmed neutron star merger occur, as detected by ligo in 2017
in a galaxy called ngc 4993, located about 130 million light-years from earth
what happens when two black holes merge
they form a single more massive black hole and emit strong gravitational waves
why are gravitational waves from black hole mergers particularly intense during the final death spiral
because their greater masses lead to much stronger emission of gravitational waves at this stage
what was significant about ligo’s detection on september 14, 2015
it provided strong evidence for the existence of black holes through signals matching supercomputer models of black hole mergers
which even releases more energy than a massive star supernova
the merger of two neutron stars emitting gravitational waves and producing rare elements like gold and platinum
how do astronomers identify extreme outbursts of energy in space
by watching for extreme outbursts across various wavelengths, including gamma rays, x-rays, and visible light using different types of telescopes simultaneously or sequentially after initial detection events like gamma-ray bursts or gravitational waves are observed by specialized instruments like ligo or fermi satellite systems respectively
what supports a white dwarf against the crush of gravity
electron degeneracy pressure
what can cause a white dwarf to explode as a supernova in a close binary system
the white dwarf’s mass reaching the white dwarf limit of 1.4 solar masses
how does hydrogen build-up on a white dwarf’s surface in a close binary system
through an accretion disk that swirls toward the white dwarf’s surface
what is a neutron star primarily composed of
neutrons
how were neutron stars first discovered
by detecting pulsars, which are rapidly spinning neutron stars emitting beans of radiation
what phenomenon can occur when a neutron star in a close binary system accretes hydrogen from its composition
x-ray bursts due to periodic helium fusion on the neutron star’s surface
what marks the boundary between our observable universe and the inside of a black hole
the event horizon
what happens to light emitted by an object as it falls closer to a black hole
it becomes increasingly redshifted until it disappears from view
what evidence supports the existence of black holes in x-ray binaries
the presence of compact objects too massive to be neutron stars
what are gamma-ray bursts most likely associated with
unusually powerful supernova explosions that may create black holes
what is believed to be one primary source of gold, platinum, and uranium in the universe
mergers of neutron stars in close binary systems emitting gravitational waves before merging
how have gravitational waves provided evidence for black hole mergers
by being directly detected from systems consisting of two merging black holes, representing strong evidence for their existence
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Flashcards (158)