Neutron Stars White dwarf Mass limit for White Dwarf


НазваNeutron Stars White dwarf Mass limit for White Dwarf
Дата конвертації06.06.2013
Розмір452 b.
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Neutron Stars


White dwarf



Mass limit for White Dwarf

  • MCh ~ 1.46 Msun



Inverse ß–decay



Degeneracy Pressure

  • Pauli exclusion principle

  • Heisenberg uncertainty priniple

  • P = nvp

  • Distribution function for fermions

  • Pressure :



Simple Calculation!

  • If M ~ 2 Msun then R ~ 15 Km



H-R Position



Features



Features

  • Radius ~ 10 km



Features

  • Radius ~ 10 km

  • Period ~ 0.001s – 6.0 s

  • The Sun at 15 km would rotate 700 times per second



Features

  • Radius ~ 10 km

  • Period ~ 0.001s – 6.0 s

  • Density ~ 1014g/cc

  • 1012 times higher than the density

  • in the Sun





Features

  • Radius ~ 10 km

  • Period ~ 0.001s – 6.0 s

  • Density ~ 1014g/cc

  • Gravity ~ 2×1012 m/s2

  • 2×1011 times that of Earth



Features

  • Radius ~ 10 km

  • Period ~ 0.001s – 6.0 s

  • Density ~ 1014g/cc

  • Gravity ~ 2×1012 m/s2

  • gravitational redshift



Features

  • Radius ~ 10 km

  • Period ~ 0.001s – 6.0 s

  • Density ~ 1014g/cc

  • Gravity ~ 2×1012 m/s2

  • gravitational redshift



Features

  • Radius ~ 10 km

  • Period ~ 0.001s – 6.0 s

  • Density ~ 1014g/cc

  • Gravity ~ 2×1012 m/s2

  • gravitational redshift

  • escape velocity ~ 0.4c – 0.8c

  • if an average human were to encounter a neutron star, they would impact with roughly the energy yield of a 100 megaton nuclear explosion



Features

  • Radius ~ 10 km

  • Period ~ 0.001s – 6.0 s

  • Density ~ 1014g/cc

  • Gravity ~ 2×1012 m/s2

  • Magnetic field ~ 1012 Gauss

  • Magnetic field of Earth at poles ~ 0.6 Gauss



Features

  • Radius ~ 10 km

  • Period ~ 0.001s – 6.0 s

  • Density ~ 1014g/cc

  • Gravity ~ 2×1012 m/s2

  • Magnetic field ~ 1012 Gauss

  • Earth with R = 5m could produce such magnetic field.



Mass Limit

  • By Oppenheimer & Volkoff

  • MOV ~ 3.2 Msun



Mass Limit

  • Tolman-Oppenheimer-Volkoff (TOV) equation



More Mass!



Neutron Star Pizza



Core

  • Superfluidity: degenerate neutrons can flow without any friction.

  • Superconductivity: electrical currents inside the neutron star can travel around without experiencing any electrical resistance. Therefore, once you start an electrical current it keeps going forever.

  • Neutronium

  • Strange matter





Physics in Core

  • We need three physical theories to understand their dense interiors:

  • Relativity theory is needed because so much mass occupies such a small space that space-time is warped.

  • Nuclear theory is needed both because the crust on neutron stars is made of iron and nickel nuclei, and the pressure in the interior is so great that nuclei are torn apart into their individual nucleons.

  • Quantum mechanics is needed to properly understand this microworld.



History

  • 1930 Lev Davidovic Landau

  • 1931 S. Chandrasekhar

  • 1932 Sir James Chadwick

  • 1933 Walter Baade & Fritz Zwicky

  • 1939 J. R. Oppenheimer & G. M. Volkoff

  • 1967 Jocelyn Bell & Anthony Hewish

  • 1971 Riccardo Giacconi





Supernova 1987a



Crab Nebula





Neutron Stars

  • Pulsars

  • X-ray Brusters

  • Magnetars



Pulsars

  • In 1967 at Cambridge University, Jocelyn Bell observed a strange radio pulse that had a regular period of 1.3373011 seconds



Pulsars



Pulsar or Neutron Star



Pulsars

  • Lighthouse



Sound of Pulsars!



PSR B0329+54

  • This pulsar is a typical, normal pulsar, rotating with a period of 0.714519 seconds, i.e. close to 1.40 rotations/sec



PSR B0833-45, The Vela Pulsar

  • This pulsar lies near the centre of the Vela supernova remnant, which is the debris of the explosion of a massive star about 10,000 years ago. The pulsar is the collapsed core of this star, rotating with a period of 89 milliseconds or about 11 times a second.



PSR B0531+21, The Crab Pulsar

  • This is the youngest known pulsar and lies at the centre of the Crab Nebula, the supernova remnant of its birth explosion, which was witnessed by Europeans and Chinese in the year 1054 A.D. as a day-time light in the sky. The pulsar rotates about 30 times a second.



PSR J0437-4715

  • This is a recently discovered millisecond pulsar, an old pulsar which has been spun up by the accretion of material from a binary companion star as it expands in its red giant phase. The accretion process results in orbital angular momentum of the companion star being converted to rotational angular momentum of the neutron star, which is now rotating about 174 times a second



PSR B1937+21

  • This is the fastest known pulsar, rotating with a period of 0.00155780644887275 seconds, or about 642 times a second. The surface of this star is moving at about 1/7 of the velocity of light



Binary Pulsars



X-Ray Blusters





Magnetar

  • Soft Gamma Repeater (1979)

  • (SGRs)



Magnetar

  • Theory by Dr.Robert Duncan (1992)

  • A nuetron star with a super-strong magnetic field

  • SGR 1806-20 T=7.5 s

  • magnetic field strength of about 800 trillion Gauss

  • Normal radio pulsars reach about 1 trillion to 5 trillion Gauss



Schrödinger

  • Schrödinger’s equation for electron in electromagnetic field:



Magnetar

  • At the surface of the star a chunk of magnetizable metal like iron would feel a force equal to 150 million times the Earth's gravitational pull on it

  • magnetism itself can keep the star hot - about 10 million degrees C



Recent Expriment

  • The RHIC relativistic nuclear collider at Brookhaven and the LHC hadron collider at CERN Geneva were built precisely to investigate the micro-world which inhabits neutron star interiors.



Neutron Star in IRAN



Summary

  • Neutron stars are the most interesting objects that observed…



References



By

  • Hossein Alisafaee

  • 8111017

  • Automn 1383

  • THANKS ALL



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