Astronomers have identified more and more black holes in recent years by using x-ray imaging. If black holes are supposed to be black and not emit light, where are the x rays coming from?

a. The accretion disk is full of accelerating atoms, which emit electromagnetic radiation as they accelerate.
b. The friction within the accretion disk heats the gas to very high temperatures, and the gas emits x rays according to its characteristic spectrum.
c. Hawking radiation not captured by the black hole knocks out K shell electrons within the accretion disk and the matter emits characteristic x rays.
d. Scientists suspect that many of the supposed black holes are indeed neutron stars that emit x-ray radiation.
e. Gravitational waves coming from the black hole are thought to interact with matter in the accretion disk, exciting many of the atoms into producing x rays.


b.
It has been well established that x rays are emitted by black holes. Scientists suspect that the radiation comes from superheated gas in orbit "falling into" the black hole.

Physics & Space Science

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