dec.2 astronomy

Introduction to Black Holes

• Fundamental concepts of black holes in the context of gravitational theory.

• General Relativity:

  • Describes distances in spacetime near massive bodies.

  • Explains phenomena like the precession of Mercury, deflection of light, gravitational time dilation, and gravitational waves.

Black Hole Characteristics

• Singularities and event horizons, rotating and charged black holes, the "No Hair" theorem, Hawking radiation, tides near black holes, detection methods.

Schwartzschild Solution

• Metric for a static black hole; the event horizon marks the boundary between outside and inside the black hole.

• For a non-rotating black hole, spacetime has infinite curvature at the singularity.

  • Cosmic censorship cloaks singularities behind event horizons.

  • Roger Penrose's work on the presence of singularities inside black holes.

Charged Black Holes

• Reissner and Nordström's equations describe charged black holes; a second event horizon forms with added charge.

Kerr Black Holes

• Roy Kerr's solution for rotating black holes gains importance in black hole physics.

• Characteristics include:

  • Flat ring singularity

  • Dragged spacetime (Lense-Thirring effect)

  • Two photon spheres and ergosphere.

  • Kerr black holes are considered the most likely black holes to exist in nature.

The "No Hair" Theorem

• States that black holes can only be characterized by their mass, spin, and charge.

Stephen Hawking's Contributions

• Showed that black holes radiate and that their event horizon area must increase, linking concepts of entropy (Second Law of Thermodynamics).