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Topic: Degeneracy pressure

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Neutron degeneracy pressure

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	Pressure, Degeneracy, Exchange Interaction, Neutron Stars, Atoms, Etc.
		The pressure in a degenerate Fermi fluid is higher than it would be in a non-degenerate or non-fermionic fluid under comparable conditions of density and temperature.
		Pressure might have been on the list in the early 19th century, but it was stricken when people realized it can be fully explained in terms of the other items on the list, via “kinetic theory”.
		It is evident from equation 4 that for a nonrelativistic gas, the energy (and hence pressure) depend inversely on the mass of the particles.
	www.av8n.com /physics/degeneracy.htm (2811 words)

	waltner (Site not responding. Last check: 2007-10-08)
		There is no lower limit on pressure for the bosons in the system as the Bose-Einstinian statistical distribution function has zero as the lower bound as the temperature approaches zero.
		Thus we must balance the gravitational gradient with that of the pressure where the pressure gradient is made up of a pressure from the gas as well as a pressure exerted by the photons.
		The program was allowed to calculate the pressure given differing temperatures and the chemical potential required to make the number density such that it made the degeneracy the specified amount.
	electron4.phys.utk.edu /sa/1997/waltner.html (1937 words)

	Degenerate matter -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-10-08)
		The pressure maintained by a body of degenerate matter is called the degeneracy pressure, and arises because the Pauli principle forbids the constituent particles from occupying identical quantum states.
		Unlike (additional info and facts about gases) gases, degenerate matter is difficult to compress and the volume of degenerate matter does not change much in response to changes in temperature or pressure.
		Exotic examples of degenerate matter include (additional info and facts about neutronium) neutronium, (additional info and facts about strange matter) strange matter, (additional info and facts about metallic hydrogen) metallic hydrogen and (A faint star of enormous density) white dwarf matter.
	www.absoluteastronomy.com /encyclopedia/d/de/degenerate_matter.htm (152 words)

	LP 768-500
		Degeneracy is a state of matter in which the only forces acting are those from quantum effects.
		Degeneracy occurs following gravitational collapse in which the electrons are stripped from their host atoms, thus only electrons and atomic nuclei can only exist in a closely packed highly dense state.
		It is then the degeneracy pressure exerted by the tightly packed neutrons that balances the gravitational force.
	www.weblore.com /richard/lp_768-500.htm (440 words)

	Degenerate matter - Wikipedia, the free encyclopedia
		Degenerate matter is matter which has sufficiently high density that the dominant contribution to its pressure arises from the Pauli exclusion principle.
		Unlike gases, degenerate matter is difficult to compress and the volume of degenerate matter does not change much in response to changes in temperature or pressure.
		Exotic examples of degenerate matter include neutronium, strange matter, metallic hydrogen and white dwarf matter.
	en.wikipedia.org /wiki/Degenerate_matter (212 words)

	White Dwarf Information - Articles Free (Site not responding. Last check: 2007-10-08)
		The maximum mass of a white dwarf, beyond which degeneracy pressure can no longer support it, is about 1.4 solar masses.
		When this limit is exceeded, the pressure exerted by electrons is no longer able to balance the force of gravity, and the star continues to contract, eventually forming a neutron star.
		In the 1930's the explanation is given as a quantum mechanical effect: the weight of the white dwarf is supported by the pressure of electrons (electron degeneracy), which only depends on density and not on temperature.
	www.articlesfree.com /index.php?title=White_dwarf (1245 words)

	EXCESS MASS STRESS (Site not responding. Last check: 2007-10-08)
		The degeneracy pressure is reduced by the clustering behavior of bosons and of pairs of fermions.
		Therefore during periods of intensified clustering, i.e., orogenic episodes, the degeneracy pressure is reduced and the Earth tends to contract.
		When the degeneracy pressure of electrons exceeds the gravitational pressure of nucleons, the core tends to expand and the surface stress is tensional.
	www.geocities.com /CapeCanaveral/Launchpad/8098/Excess-mass-stress.htm (5936 words)

	Chapter 14 Review Answers (Site not responding. Last check: 2007-10-08)
		Degeneracy pressure is a result of the exclusion principle which limits the number of electrons that can be put into a given volume.
		The pressure of a degenerate gas is related to the density rather than the temperature and volume as in an ordinary gas.
		As the core collapses and heats, the pressure may be strong enough to drive together protons and electrons to form neutrons.
	www.usd.edu /phys/courses/kellerastronomy/text/review/review14.html (331 words)

	White Dwarfs
		A white dwarf is supported by a different type of pressure (not dependent on the temperature of the white dwarf): electron degeneracy pressure.
		(Remember the electron degeneracy pressure which supports a white dwarf is not dependent on T; thus, hydrostatic equilibrium is maintained even as the white dwarf cools.) Since T decreases and R is constant, the luminosity L decreases.
		The pressure within a white dwarf depends only on density, not on temperature; to maintain the tremendous pressures required to support a massive white dwarf, the white dwarf must have a very great density.
	www.stormpages.com /swadhwa/stellarevolution/lecture18.htm (1184 words)

	ASTR 498N Lecture 7
		In every government on earth is some trace of human weakness, some germ of corruption and degeneracy, which cunning will discover, and wickedness insensibly open, cultivate and improve.
		The pressure may be calculated from the fundamental integral (OandC Eq.
		They are equations of state for electron pressure in a perfect, completely degenerate electron gas.
	www.astro.umd.edu /~drabin/Lecture7.htm (406 words)

	The Cosmic Perspective Chapter 22 -- Summary (Site not responding. Last check: 2007-10-08)
		In the corpse of a low-mass star, gravitational forces compress the matter until electron degeneracy pressure balances gravity, and the star ends its days as a white dwarf.
		In the corpse of a high-mass star, electron degeneracy pressure is too weak to resist gravity.
		Because electron degeneracy pressure is too weak to balance gravity in objects heavier than 1.4 times the mass of the Sun, there can be no white dwarfs above this mass limit.
	occawlonline.pearsoned.com /bookbind/pubbooks/bennett2_awl/chapter22/objectives/deluxe-content.html (623 words)

	[No title]
		Degeneracy pressure is when the electrons (or neutrons) are so closely packed together that they cannot get any closer, due to the exclusion principle.
		The core contraction continues until it reaches electron degeneracy, and electron degeneracy pressure is then supporting the core.
		Because of the high temperatures, the thermal pressure increases, causing the expansion of the envelope of the star.
	www.astro.lsa.umich.edu /~rstanek/w02/hmwk7.html (882 words)

	General Science 2310 - White Dwarfs (Site not responding. Last check: 2007-10-08)
		The total pressure in a white dwarf is dominated by electron degeneracy pressure.
		At any rate, the pressure in a white dwarf is nearly constant throughout, meaning that if you were to visit one, you would see the surface as a distinct almost solid crust.
		As the density increases past the point where the electrons are moving close to the speed of light, the degeneracy pressure becomes less sensitive to changes in pressure.
	www.lakeheadu.ca /~physwww/courses/Astro/2330/Death/Dwar.htm (590 words)

	Lucia M. Franco Research Page: The Fight Against Gravity
		Degeneracy pressure exists only when particles come too close to one another.
		Degeneracy pressure is not originated by using a fuel source.
		Once the WD or NS are supported by degeneracy pressure, the situation is stable.
	astro.uchicago.edu /home/web/lucia/research/fight_gravity/allinone.html (667 words)

	No Title
		The pressure to resist further gravitational collapse is then supplied by the electrons - it is termed degeneracy pressure.
		The righthand side is the attractive gravitational force on a spherical shell at radius r and this is then equated to the pressure gradient resisting compression.
		Providing the initial mass is not too high this neutron gas can then halt the gravitational collapse using now neutron degeneracy pressure (which because of the larger mass of a neutron to an electron is significantly larger than the electron pressure).
	www.phy.syr.edu /courses/PHY307.01Fall/grad_proj/dwarf/star/star.html (718 words)

	General Science 2310 - Evolution of Low and Intermediate Mass Stars
		In a degenerate electron gas, the gas pressure is dominated by electron degeneracy pressure rather than thermal pressure.
		The only way to increase degeneracy pressure is to increase the particle density.
		This explosive behaviour occurs because the pressure is dominated by degeneracy pressure so that increasing temperatures will not cause the core to expand and cool as it would in a main sequence star.
	www.lakeheadu.ca /~physwww/courses/Astro/2330/Evolve/LowM.htm (1151 words)

	sciforums.com - Degeneracy pressure and Fermions
		Degeneracy pressure for non-relativistic electrons is given as p~1/((d^2)(Me)) where d is the mean inter electron distance and Me is electron mass, a similar equation is given for neutron degeneracy pressure p~1/((d^2)(Mn)).
		What I'm wondering is: does anyone have of a good reason for all Fermions degeneracy pressures not to be represented by the general equation p~1/((d^2)(Mf))?
		I see no good reason why a single general equation couldn't be applied to the degeneracy pressures of all Fermions.
	www.sciforums.com /showthread.php?p=1083 (295 words)

	Archive of Astronomy Questions and Answers (Site not responding. Last check: 2007-10-08)
		These stellar cinders are supported by electron degeneracy pressure (white dwarfs) and neutron degeneracy pressure (neutron stars) which are two very different mechanisms.
		Both forces are expressed by essentially the same formula, except that the strong nuclear force is 100 times more than the electromagnetic force, and this causes the size of the neutron star to be much smaller than a white dwarf (10,000 km vs 20 km).
		Even though the pressure comes from the light-weight electrons in white dwarfs, the mass of the body is still determined by the number of protons and neutrons.
	www.astronomycafe.net /qadir/q2228.html (254 words)

	[No title]
		Degeneracy pressure is a result of a limit in quantum mechanics known as the Pauli Exclusion Principal.
		This results in a pressure that stops contraction that is more or less the same at any temperature, even absolute zero.
		The hotter the object, the faster the particles are moving, resulting in a higher pressure.
	casa.colorado.edu /~arav/astr1120/homework/hw5_solution.doc (554 words)

	Digital Demo Room Stellar Structure and Evolution Tutorial
		The remaining carbon/oxygen core contracts to the point at which electron degeneracy pressure counteracts the inward pull of gravity.
		If the core's mass is less than about 3 solar masses, the core's neutron degeneracy pressure continues to counteract the inward pull of gravity, stabilizing it into a neutron star.
		If the core's remaining mass is greater than about 3 solar masses, not even neutron degeneracy pressure will be able to withstand the inward pull of gravity, and the core will collapse into a fl hole from which no electromagnetic radiation can escape (Chaisson and McMillan).
	rainman.astro.uiuc.edu /ddr/stellar/evolution.html (1612 words)

	Death of Low Mass Stars: White Dwarfs (Site not responding. Last check: 2007-10-08)
		The collapse of the core therefore continues until a new kind of pressure is able to support the star against gravity.
		Electron degeneracy pressure is a consequence of an important principle in quantum mechanics called the Pauli exclusion principle.
		Since degeneracy pressure is unaffected by temperature, the white dwarf does not contract as it cools; it basically cools off like a charcoal briquet, eventually becoming a cold fl dwarf.
	www.atnf.csiro.au /people/twong/ay10b/evol/node4.html (349 words)

	Astronomy Lecture Number 19
		Remember that degeneracy pressure is due to the electrons all being so close together that they have no other energy states to go into.
		This electron degeneracy exerts the pressure that keeps the star up, but when it fails the electrons are actually forced into the nucleus, all of the protons combine with the electrons to form neutrons, and the entire core becomes one big neutron nucleus!
		Such a neutron core has its own degeneracy, called neutron degeneracy, which may halt the collapse of the core, but by then the core has shrink (in a fraction of a second) from an object the size of the Earth to an object only 10 km across.
	physics.njit.edu /~dgary/202/Lecture19.html (2363 words)

	ASTR 100 Lecture 25 (27 Oct 2003)
		This means that atoms are pushed together until their electron clouds overlap, and since electrons don't like to occupy the same energy levels in the same space, some of the electrons are pushed into higher energy levels.
		As a result they exert pressure (degeneracy pressure) that prevents the collapse of the star.
		So now that they are packed tightly together in the core of the old star, their degeneracy pressure resists further collapse.
	www.astro.uiuc.edu /classes/archive/astr100/f03_lect1/lecture25_summary.html (1356 words)

	Stellar Evolution continued
		K where He fusion would start and produce the thermal pressure required to balance gravity and then work in the thermostat mode.
		Electron Degeneracy Pressure is what balances gravity in the RGB star core and EDP has a strange property in that it is more-or-less independent of temperature.
		Because the pressure in the core is due to
	www.ucolick.org /~bolte/AY4/notes10/node1.html (463 words)

	Chemistry - Chandrasekhar limit
		If the star has a mass below the Chandrasekhar limit this collapse is limited by electron degeneracy pressure, which results in a stable white dwarf.
		The Chandrasekhar limit arises from taking account of the effects of quantum mechanics in considering the behaviour of the electrons providing the degeneracy pressure supporting the white dwarf.
		In the quantum mechanical calculation the typical energies to which degeneracy pressure forces the electrons in a massive white dwarf are non-negligible relative to their rest masses and a limiting mass emerges for a self-gravitating, spherically symmetric body supported by degeneracy pressure.
	www.chemistrydaily.com /chemistry/Chandrasekhar_limit (384 words)

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