According to the no-hair theorem in astrophysics, which three properties fully determine a black hole's external field?

According to the no-hair theorem in astrophysics, which three properties fully determine a black hole's external field?

• A. Mass, Charge, and Angular Momentum
• B. Mass, Radius, and Temperature
• C. Spin, Magnetic Field, and Luminosity
• D. Size, Density, and Color

Answer: (A)

The idea being tested is that a stationary black hole’s external field is completely described by three quantities: its mass, electric charge, and angular momentum. These are the only externally observable, conserved properties that shape the spacetime outside the black hole. Mass sets the overall strength and scale of the gravitational field; charge adds the electromagnetic field surrounding the hole; and angular momentum (spin) determines frame-dragging effects and the rotational geometry (Kerr or Kerr–Newman solutions). Other supposed descriptors like radius or temperature aren’t independent external parameters. The horizon radius is determined by mass, charge, and spin; temperature arises from quantum effects (Hawking radiation) and isn’t part of the classical external field; and magnetic field or luminosity depend on the environment around the black hole, not on its intrinsic parameters. So the external field is fully determined by mass, charge, and angular momentum.

The idea being tested is that a stationary black hole’s external field is completely described by three quantities: its mass, electric charge, and angular momentum. These are the only externally observable, conserved properties that shape the spacetime outside the black hole. Mass sets the overall strength and scale of the gravitational field; charge adds the electromagnetic field surrounding the hole; and angular momentum (spin) determines frame-dragging effects and the rotational geometry (Kerr or Kerr–Newman solutions). Other supposed descriptors like radius or temperature aren’t independent external parameters. The horizon radius is determined by mass, charge, and spin; temperature arises from quantum effects (Hawking radiation) and isn’t part of the classical external field; and magnetic field or luminosity depend on the environment around the black hole, not on its intrinsic parameters. So the external field is fully determined by mass, charge, and angular momentum.