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Basics Of Astrophysics

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Homam Hosseini
Homam Hosseini

This document provides an overview of several topics in astrophysics, including: 1. It discusses stars and their properties like mass, luminosity, temperature, and the proton-proton chain reaction. 2. It covers neutrinos and their characteristics. 3. It describes neutron stars and their properties, how they are formed in supernovas, and provides some details about Supernova 1987A. 4. It discusses pulsars and their discovery, and properties of neutron stars.

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Basics of astrophysics
Stars Story  Hydrostatic equilibrium  Mass  Luminosity - Temperature
Basics Of Astrophysics
Proton – Proton Chain  As happens in the core of a typical main sequence star. 0.23% 99.77% 10-5% 15.08% 99.9% 0.1% 84.92%
Neutrino  Leptons  No electrical charge  Passes through ordinary matter
Problem  Determine the maximum size of rotating body with rotation period = 0.033 second
Basics Of Astrophysics
Basics Of Astrophysics
Neutron Stars  The core of a massive star in a supernova  Chandrasekhar limit (12.5)  Stable state  Most SNs produce NSs -> 108 – 109 NSs in universe  The T of a NS falls from 1012K to 1011 K in 2 seconds  A young NS is about 106 K
Supernova 1987A In LMC
1987A’s Timeline  Feb.23 7:35am, a total number of 24 neutrons detected  Hours later the visible SN discovered  Neutrinos and antineutrinos reached the earth synchronously : matter, antimatter and photos react the same against gravity  1987A was a blue supergiant!  Missing neutron star
1987A 1987 was discovered in Feb., but reached the brightest in Mar. AAVSO observations
Basics Of Astrophysics
Rings turning on  Months after SN  Emission lines  UV  The distance: 168,000 ly
Neutrinos in Supernovas  Direct observation of SNs is impossible Dense gas surrounds SNs, and…  Information about the inner most regions of a SN No interaction with matter  Delay of 1987 visible light  First impressions in 1987
Some Facts  Much of the visible light comes from the decay of radioactive elements produced by the supernova shock wave, and even light from the explosion itself is scattered by dense and turbulent gases.  The neutrino burst is expected to reach Earth before any electromagnetic waves (SNEWS)
So  Was the total energy released in a SN less than the energy that ionized shell emits?  99% of energy (1046 j) -> neutrinos  Where all these neutrinos come from?
Urca process  (Z-1,A) -> (Z,A) + e- + ν-e  (Z,A) + e- -> (Z-1,A) + νe  Two forms of beta decay  Baryons - Leptons  Gamow, Loosing energy (cooling), Casino Urca
Beta decay Beta Minus Beta Plus Electron Capture
Pulsars  Discovery 1967 as little green men  Neutron stars are low in luminosity (why?)
 Giant atomic nucleus  Fluid Super conductor  Magnetic dipole radiation  Spin periods of pulsars increase by time
Basics Of Astrophysics
Basics Of Astrophysics
Widescreen Test Pattern (16:9) Aspect Ratio Test (Should appear circular) 4x3 16x9

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Basics Of Astrophysics

  • 2. Stars Story  Hydrostatic equilibrium  Mass  Luminosity - Temperature
  • 4. Proton – Proton Chain  As happens in the core of a typical main sequence star. 0.23% 99.77% 10-5% 15.08% 99.9% 0.1% 84.92%
  • 5. Neutrino  Leptons  No electrical charge  Passes through ordinary matter
  • 6. Problem  Determine the maximum size of rotating body with rotation period = 0.033 second
  • 9. Neutron Stars  The core of a massive star in a supernova  Chandrasekhar limit (12.5)  Stable state  Most SNs produce NSs -> 108 – 109 NSs in universe  The T of a NS falls from 1012K to 1011 K in 2 seconds  A young NS is about 106 K
  • 11. 1987A’s Timeline  Feb.23 7:35am, a total number of 24 neutrons detected  Hours later the visible SN discovered  Neutrinos and antineutrinos reached the earth synchronously : matter, antimatter and photos react the same against gravity  1987A was a blue supergiant!  Missing neutron star
  • 12. 1987A 1987 was discovered in Feb., but reached the brightest in Mar. AAVSO observations
  • 14. Rings turning on  Months after SN  Emission lines  UV  The distance: 168,000 ly
  • 15. Neutrinos in Supernovas  Direct observation of SNs is impossible Dense gas surrounds SNs, and…  Information about the inner most regions of a SN No interaction with matter  Delay of 1987 visible light  First impressions in 1987
  • 16. Some Facts  Much of the visible light comes from the decay of radioactive elements produced by the supernova shock wave, and even light from the explosion itself is scattered by dense and turbulent gases.  The neutrino burst is expected to reach Earth before any electromagnetic waves (SNEWS)
  • 17. So  Was the total energy released in a SN less than the energy that ionized shell emits?  99% of energy (1046 j) -> neutrinos  Where all these neutrinos come from?
  • 18. Urca process  (Z-1,A) -> (Z,A) + e- + ν-e  (Z,A) + e- -> (Z-1,A) + νe  Two forms of beta decay  Baryons - Leptons  Gamow, Loosing energy (cooling), Casino Urca
  • 19. Beta decay Beta Minus Beta Plus Electron Capture
  • 20. Pulsars  Discovery 1967 as little green men  Neutron stars are low in luminosity (why?)
  • 21.  Giant atomic nucleus  Fluid Super conductor  Magnetic dipole radiation  Spin periods of pulsars increase by time
  • 24. Widescreen Test Pattern (16:9) Aspect Ratio Test (Should appear circular) 4x3 16x9