Which structure around Cygnus X-1 is directly involved in feeding matter toward the black hole?

• A. Event horizon
• B. Accretion disk
• C. Corona
• D. Dust torus

Answer: (B)

Feeding matter toward a black hole happens through an accretion disk, a rotating disk of gas that spirals inward as viscosity allows angular momentum to be transported outward and gravitational energy to be converted into heat. In Cygnus X-1, material drawn from the companion star forms this disk and becomes extremely hot, emitting strong X-rays as it loses energy while moving closer to the black hole. The event horizon is the boundary beyond which nothing can escape, not a structure that channels matter inward. The corona is a hot, tenuous region above the disk that produces high-energy photons through scattering processes, but it’s not the channel that feeds matter. A dust torus is a broader, often larger-scale ring found in some active galaxies, not the main feeding feature in this stellar-mass black hole system. Therefore, the accretion disk is the structure directly involved in feeding matter toward the black hole.