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).

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