X-rays from Cygnus X-1 are produced because particles collide and heat up to what scale?

X-rays from Cygnus X-1 are produced because particles collide and heat up to what scale?

• A. Thousands of degrees
• B. Millions of degrees
• C. Billions of degrees
• D. Hundreds of degrees

Answer: (B)

X-ray emission from Cygnus X-1 comes from gas in the accretion flow around the black hole that is heated to extremely high temperatures. As matter from the companion star spirals inward, gravitational energy is released and, through friction and shocks in the disk, this energy heats the gas to about a few million kelvin. At these temperatures, the thermal radiation peaks in the X-ray part of the spectrum, so the hot, X-ray photons dominate what we observe. That’s why the scale is millions of degrees—the inner parts of the accretion disk around a stellar‑mass black hole reach temperatures of this order, producing the X-rays we detect. Very hot gas at billions of kelvin would also emit X-rays, but the typical temperatures for Cygnus X-1’s inner disk are in the millions of kelvin range, which aligns with the observed X-ray emission.

X-ray emission from Cygnus X-1 comes from gas in the accretion flow around the black hole that is heated to extremely high temperatures. As matter from the companion star spirals inward, gravitational energy is released and, through friction and shocks in the disk, this energy heats the gas to about a few million kelvin. At these temperatures, the thermal radiation peaks in the X-ray part of the spectrum, so the hot, X-ray photons dominate what we observe. That’s why the scale is millions of degrees—the inner parts of the accretion disk around a stellar‑mass black hole reach temperatures of this order, producing the X-rays we detect. Very hot gas at billions of kelvin would also emit X-rays, but the typical temperatures for Cygnus X-1’s inner disk are in the millions of kelvin range, which aligns with the observed X-ray emission.