Les Trous Noirs Astrophysiques Pierre-Olivier Petrucci Institut de Planétologie et d’Astrophysique de Grenoble
Outline • Black holes: generalities • The different types of astrophysical black holes • Black hole environments (accretion disk, corona, jets,…) • A promising future
Black Holes Generalities
Newton and the Gravitation Law m R M Nuit des Equinoxes, 23 Mars 2013
Newton and the Gravitation Law m R F grav G ravitational force ! M F grav = m G M g = G M avec R 2 R 2 (gravitational) Constant gravitational acceleration On Earth g ≈ 10 m.s -2 G = 6 . 67384 × 10 − 11 m 3 .kg − 1 .s − 2 Nuit des Equinoxes, 23 Mars 2013
Escape Velocity The escape velocity can be computed from the Newton theory: r M √ 2 G v esc = R M R
Escape Velocity The escape velocity can be computed from the Newton theory: r M √ 2 G v esc = R M R
Escape Velocity The escape velocity can be computed from the Newton theory: r M √ 2 G v esc = R Numerical application ! - for the Earth: ! M earth =6 10 24 kg, R earth = 6400 km ⇒ v esc = 11 km/s ! M - for the sun: R M sun =2 10 30 kg, R sun = 700 000 km ⇒ v esc = 615 km/s !
Black Hole Concept An astrophysical object of mass M has a escape velocity v esc = c if its radius R is smaller than r R < R lim = 2 G M ➙ √ v esc = 2 G c 2 M = 2 R g R R lim =Schwarzschild radius R g =gravitationnal radius (same limit found from GR equations)
Black Hole Concept An astrophysical object of mass M has a escape velocity v esc = c if its radius R is smaller than r R < R lim = 2 G M ➙ √ v esc = 2 G c 2 M = 2 R g R R lim =Schwarzschild radius R g =gravitationnal radius Then even light cannot escape ! (same limit found from GR equations) Numerical application ➡ for the Earth, R lim = 9 mm ! ➡ for the Sun, R lim = 3 km
Gravitation A huge source of energy M R
Gravitation A huge source of energy To lift a masse m at a height h above a celestial body of radius R and mass M, we need to provide: M R
Gravitation A huge source of energy To lift a masse m at a height h above a celestial body of radius R and mass M, we need to provide: F grav = G Mm R 2 = R lim h Rmc 2 E grav = F grav h 2 R M R
Gravitation A huge source of energy To lift a masse m at a height h above a celestial body of radius R and mass M, we need to provide: F grav = G Mm R 2 = R lim h Rmc 2 E grav = F grav h 2 R Numerical applications: m=1kg, h=1m • E grav = 10 Joules on Earth • E grav = 300 Joules on the Sun M For a black hole R=R lim : R • E grav = 10 12 Joules on a black hole of 10 M sun
Gravitation A huge source of energy To lift a masse m at a height h above a celestial body of radius R and mass M, we need to provide: F grav = G Mm The more compact the object (R → R lim ) the R 2 = R lim h larger E grav ! Rmc 2 E grav = F grav h 2 R Numerical applications: m=1kg, h=1m Some astrophysical objects radiate a so • E grav = 10 Joules on Earth large luminosity that the presence of a • E grav = 300 Joules on the Sun M black hole appears very likely! For a black hole R=R lim : R • E grav = 10 12 Joules on a black hole of 10 M sun
Rotating Black Hole A rotating BH is smaller than a non rotating one… Non rotating Rotating Event horizon Ergosphere Schwarzschild Kerr R EH =R lim R lim /2<R EH <R lim The more the BH rotates, the larger E grav !
Funny effects… Gravitational lensing
Funny effects… Gravitational lensing Amplified close to a black hole
Funny effects… Gravitational lensing Amplified close to a black hole
A wrong Idea… Black hole does not always mean extreme density Black hole « density » (g/cm 3 ) Water density Black hole mass (M sun )
A wrong Idea… Black hole does not always mean extreme density M BH ~ 10s M sun Black hole « density » > 10 10 kg/cm 3 Strong tidal effects (g/cm 3 ) Water density Black hole mass (M sun )
A wrong Idea… Black hole does not always mean extreme density M BH ~ 10s M sun Black hole « density » > 10 10 kg/cm 3 Strong tidal effects (g/cm 3 ) M BH > 10 8 M sun Water Less dense than water density Small tidal effects Black hole mass (M sun )
The Different Types of Astrophysical Black Holes
Two Main Types of Black holes ����������������������������� ������������������� ������������������������ Courtesy: Colpi (2018) Number of objects Mass M/M sun �������������� �������������
Two Main Types of Black holes ����������������������������� ������������������� ������������������������ Courtesy: Colpi (2018) Number of objects Stellar mass BH ! Origin: Final product of dead stars Mass M/M sun �������������� �������������
Two Main Types of Black holes ����������������������������� • Binary system black hole + (donor) Microquasar star ������������������� ������������������������ Courtesy: Colpi (2018) Number of objects Stellar mass BH ! Origin: Final product of dead stars Mass M/M sun �������������� �������������
Two Main Types of Black holes ����������������������������� • Binary system black hole + (donor) Microquasar star • The matter of the star spirals around the black hole ������������������� ������������������������ Courtesy: Colpi (2018) Number of objects Stellar mass BH ! Origin: Final product of dead stars Mass M/M sun �������������� �������������
Two Main Types of Black holes ����������������������������� • Binary system black hole + (donor) Microquasar star • The matter of the star spirals around the black hole ������������������� ������������������������ • Large amount of energy released at high energy, close to the black hole Courtesy: Colpi (2018) Number of objects Stellar mass BH ! Origin: Final product of dead stars Mass M/M sun �������������� �������������
Two Main Types of Black holes ����������������������������� • Binary system black hole + (donor) Microquasar star • The matter of the star spirals around the black hole ������������������� ������������������������ • Large amount of energy released at high energy, close to the black hole Courtesy: Colpi (2018) • Part of the matter feeds the black Number of objects hole but part of it is ejected Stellar mass BH ! Origin: Final product of dead stars Mass M/M sun �������������� �������������
Two Main Types of Black holes ����������������������������� ������������������� ������������������������ Courtesy: Colpi (2018) Number of objects Mass M/M sun �������������� �������������
Two Main Types of Black holes ����������������������������� ������������������� ������������������������ Courtesy: Colpi (2018) Number of objects Super Massive BH ! Origin: Not completely understood Mass M/M sun �������������� �������������
Two Main Types of Black holes ����������������������������� • Most of the galaxies have a super Active Galactic Nuclei massive black hole in their center ������������������� ������������������������ Courtesy: Colpi (2018) Number of objects Super Massive BH ! Origin: Not completely understood Mass M/M sun �������������� �������������
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