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Topic: Electron degeneracy pressure

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Neutron degeneracy pressure

White dwarf

White dwarf

	Electron degeneracy pressure - Wikipedia, the free encyclopedia
		Electron degeneracy pressure is a force caused by the Pauli exclusion principle, which states that two electrons cannot occupy the same quantum state at the same time.
		When the pressure due to the "Heisenberg speed" exceeds that of the pressure from the thermal motions of the electrons, the electrons are labeled as degenerate.
		Electron degeneracy pressure is the pressure that keeps a white dwarf star from collapsing.
	en.wikipedia.org /wiki/Electron_degeneracy_pressure (349 words)

	Degenerate matter - Wikipedia, the free encyclopedia
		In metals it is useful to treat the conduction electrons alone as a degenerate, free electron gas while the majority of the electrons are regarded as occupying bound quantum states.
		As protons and electrons occur in roughly equal numbers in most forms of matter, proton degeneracy is usually modelled as a correction to the equations of state of electron-degenerate matter, as opposed to the dominant source of degeneracy pressure (which would require proton-degenerate matter that was free of electrons).
		Neutron degeneracy is analogous to electron degeneracy and is demonstrated in neutron stars, which are supported by the pressure from a degenerate neutron gas.
	en.wikipedia.org /wiki/Degenerate_matter (1764 words)

	Physics 408 Exam 1
		Neutron degeneracy pressure arises when neutrons are so close that their quantum states begin to overlap.
		The combined pressure from neutron degeneracy pressure and the strong nuclear force prevent further gravitational collapse of a neutron star if the remaining supernova core (neutron star) is less than 2-3 solar masses.
		In a white dwarf star it is electron degeneracy pressure that is preventing gravity from collapsing the star.
	www.calpoly.edu /~rechols/6edastro102/astro112ch23sol.html (470 words)

	White Dwarfs and Electron Degeneracy
		They collapse, moving down and to the left of the main sequence until their collapse is halted by the pressure arising from electron degeneracy.
		Electron degeneracy is a stellar application of the Pauli Exclusion Principle, as is neutron degeneracy.
		Chandrasekhar was interested in the final states of collapsed stars as determined by electron degeneracy and had used the work of Arthur S. Eddington and Ralph H. Fowler to begin his calculations.
	hyperphysics.phy-astr.gsu.edu /hbase/astro/whdwar.html (729 words)

	White Dwarf
		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.
		87, 114-122) using the electron degenerate pressure a few months after the formulation of the Fermi-Dirac statistics for an electron, on which the electron pressure is based.
	www.juliantrubin.com /encyclopedia/astronomy/whitedwarf.html (1494 words)

	Chapter 14 Review Answers (Site not responding. Last check: 2007-11-03)
		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.
		A neutron forms when the electron pressure is not strong enough the halt the collapse of a massive star.
	www.usd.edu /phys/courses/kellerastronomy/text/review/review14.html (331 words)

	Shari.com: PHYS 1412: Chapter 17
		Electron degeneracy pressure is pressure that comes from densely packed electrons that can't condense further whereas with neutron degeneracy pressure the pressure comes from densely packed neutrons.
		Since that isn't possible, at this point the electron degeneracy pressure loses the fight against gravity and the star collapses into a neutron star.
		Degeneracy pressure isn't able to stop gravity so the star collapses, experiences carbon fusion and flash, and explodes completely.
	www.shari.com /2002/03/phys_1412_chapt.html (1333 words)

	Chandrasekhar limit - QuickSeek Encyclopedia (Site not responding. Last check: 2007-11-03)
		Electrons, being fermions, cannot be at equal energy levels, so that, when an electron gas is cooling down, it is impossible for them to be given all minimal energy.
		Plenty of electrons will have to stay at higher energy levels and will thus give a certain pressure, which is purely quantum mechanical in its nature.
		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.
	chandrasekharlimit.quickseek.com (449 words)

	The Sirius Research Group
		In the configuration of the electrons, its electrons occupy the 4s-orbital and the 3d-orbital.
		While the excited electrons may not be able to radiate their energy in a quantum form, as in the case of our Sun, it is possible that their energy is emanated in a much more coherent manner.
		Since the electron degeneracy pressure is by no means stable, and given the extreme density of the atoms, the entire core of Sirius B could act (oscillate) like a giant "crystal".
	siriusresearchgroup.com /articles/ogo5.shtml (1940 words)

	[No title] (Site not responding. Last check: 2007-11-03)
		Very massive stars have massive cores, which cannot be supported by their electron degeneracy pressure after nuclear burning stops.
		Less massive stars can be supported by degeneracy pressure and leave behind white dwarfs in planetary nebula ejections.
		Electrons "do not like" to be in the same position and with the same velocity as other electrons.
	www.astro.soton.ac.uk /~tjm/homework3_answers (572 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)

	Death of Low Mass Stars: White Dwarfs (Site not responding. Last check: 2007-11-03)
		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)

	Lecture 16 - Stellar Evolution (3/16/99)
		The electrons and nuclei of the ionized gas are squeezed together tighter and tighter.
		When the core contracts to the point of degeneracy, the pressure is no longer supplied by the temperature but by the electron degeneracy.
		Furthermore, if you add heat into this degenerate gas the pressure does not increase since the heat goes into the nuclei motions, not the electrons (which are jammed into the parking lot and moving one means moving all in the way or blasting it all the way to the free spaces at the edge).
	www.aoc.nrao.edu /~smyers/courses/astro12/L16.html (3298 words)

	Death of High Mass Stars: Neutron Stars (Site not responding. Last check: 2007-11-03)
		Hydrostatic equilibrium predicts that for a star supported by gas pressure (P=nkT), the larger the mass, the higher the temperature at the center of the star must be to support that mass.
		In the process of the collapse, many of the electrons in the core are squeezed so tightly with the nuclei that they merge with protons to become neutrons.
		This reduces the electron degeneracy pressure further and accelerates the collapse.
	physics.ship.edu /~mrc/pfs/108/node6.htm (420 words)

	[No title] (Site not responding. Last check: 2007-11-03)
		The pressure at the core is larger in high mass stars, this means the temperatures are higher, and the core of the star is larger---the region fusing hydrogen is much larger, and a larger fusing area means that there is more energy output.
		The pressure and temperature go up in the core, and simultaneously, a shell of hydrogen burning is formed, as well as a core that is fusing helium into carbon.
		Neutron pressure is the last available source to balance gravity--if gravity is so strong that this pressure is overwhelmed, there is nothing to stop the collapse of the core of a massive star.
	ganymede.nmsu.edu /tharriso/ast110/class19.html (2108 words)

	Science Partners Science Fair for Grownups: L. Munoz-Franco poster
		Stars spend their lives in a constant tug of war between the force of gravity trying to compress their material as much as possible and gas pressure trying to expand the hot material that is undergoing fusion in their center.
		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/partners/starsdie.html (1424 words)

	Lucia M. Franco Research Page: The Fight Against Gravity: Page 2.
		Degeneracy pressure exists only when particles come too close to one another.
		Degeneracy pressure occurs for particles called fermions: electrons, protons, neutrons.
		This page and those that it links to are the sole responsibility of their author and in no way represent the ideas, intentions or policies of the Astronomy and Astrophysics Department at the University of Chicago.
	astro.uchicago.edu /home/web/lucia/research/fight_gravity/e-degeneracy.html (137 words)

	Archive of Astronomy Questions and Answers (Site not responding. Last check: 2007-11-03)
		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)

	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)

	electron degenerate matter
		A form of degenerate matter in which the weight of overlying material tries to force all of the electrons surrounding the atomic nucleus into the lowest energy quantum state.
		The electrons resist, because of the Paul exclusion principle, and so exert a pressure, known as degenerate electron pressure or electron degeneracy pressure, that halts further collapse.
		However, beyond this critical mass, gravity overwhelms the degeneracy pressure and results in further collapse.
	www.daviddarling.info /encyclopedia/E/electron_degenerate_matter.html (156 words)

	Assignments (Site not responding. Last check: 2007-11-03)
		The high density of the helium core has resulted in an electron degenerate gas which is a very good thermal conductor and has an outward pressure independent of temperature.
		But the increase in core temperature due to helium burning does not increase the electron degeneracy pressure and hence does not stall the contraction of the core.
		At the point when the core is supported from further collapse by electron degeneracy pressure, it is said to be a white dwarf star.
	www.umsl.edu /~bwilking/assign/12nov01.html (915 words)

	Stellar Evolution continued
		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.
		But, because EDP is independent of temperature, when He fusion starts, it is like a bomb going off.
		Because the pressure in the core is due to
	www.ucolick.org /~bolte/AY4/notes10/node1.html (463 words)

	Black Holes (Site not responding. Last check: 2007-11-03)
		The internal structure of a star is maintained by the balance between the outward internal pressure and the inward gravitational squeeze inward.
		But he noted that for large compression (large densities), the electrons are compressed in their cells to such an extent, that they speed up and their speeds approach the speed of light.
		where the electron degeneracy pressure cannot withstand gravity, the electron gas is compressed, but the neutrons of the nucleus can balance gravity (protons in the nucleus are converted into neutrons by combining with an equal number of electrons).
	www.5clir.org /BlackHoles.html (2645 words)

	White Dwarfs (Site not responding. Last check: 2007-11-03)
		A white dwarf is supported by a different type of pressure (not dependent on the temperature of the white dwarf): electron degeneracy pressure.
		Hence, the pressure exerted by the electrons remains constant as the temperature falls.
		(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.
	www.stormpages.com /swadhwa/stellarevolution/lecture18.htm (1196 words)

	Neutron Degeneracy (Site not responding. Last check: 2007-11-03)
		When neutrons are packed together, as they are in a neutron star, the number of available low energy states is too small and many neutrons are forced into high energy states.
		Because the pressure arises from this quantum mechanical effect, it is insensitive to temperature, i.e., the pressure doesn't go down as the star cools.
		Similar to electron degeneracy pressure but, because the neutron is much more massive than the electron, neutron degeneracy pressure is much larger and can support stars more massive than the Chandrasekhar mass limit.
	www.astro.virginia.edu /~jh8h/glossary/neutrondegen.htm (121 words)

	Unit 9 (Site not responding. Last check: 2007-11-03)
		Discuss the concept of electron degeneracy and how it leads to the Chandrasekhar limit for a white dwarf.
		The star will contract to the point where electrons and protons are next to each other (the normal situation in atoms or ions in a gas has electrons at great distances from protons).
		If 1.4 solar masses is exceeded, the forces due to electron degeneracy pressure are not great enough to overcome the gravitational forces attempting to push electrons into protons.
	www.phyast.pitt.edu /Resources/Education/classes/astro89/unit09.htm (1447 words)

	Chandra :: Educational Materials :: Stellar Evolution :: Stellar Evolution - Cycles of Formation and Destruction (Site not responding. Last check: 2007-11-03)
		Once the Chandraskhkar Limit is reached, the electron degeneracy pressure of the atoms within the core is no longer able to stop to further collapse of the star; radiation pressure is no longer able to support the core against gravity and the iron core collapses.
		Neutron stars have passed the 1.4 solar mass Chandrasekhar limit, and are not held in equilibrium by electron degeneracy pressure.
		The repulsive force between electrons is not strong enough to balance gravity in a star that begins with more than ~8 solar masses and has a core remnant between 1.4 and 2.5 solar masses.
	chandra.harvard.edu /edu/formal/stellar_ev/story/index11.html (705 words)

	MCC PS 100 Homework.ch.20-21
		If the remaining mass of the core is less than 1.4 solar masses, the pressure from the degenerate electrons (called electron degeneracy pressure) is enough to prevent further collapse.
		Core masses between 1.4 and 2.9 solar masses overcome electron degeneracy pressure and collapse to form neutron stars, a star that is essentially one gigantic nucleus no larger than the size of a city.
		But, to what extent is determined by the mass and the relative pressures of the quantum mechanical forces, electron and neutron degeneracy pressure.
	www.edu-observatory.org /mcc/homework/homework.ch.20-21/homework.ch.20-21.html (2008 words)

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