Multiple Choice
Why is Cygnus X-1 thought to be a black hole?
A) Cygnus X-1 emits X-rays that flicker on timescales of 1/100 second, a unique characteristic of a black hole.
B) No light has ever been observed to come from Cygnus X-1.
C) Cygnus X-1 is smaller than Earth, but its mass is too large to be a neutron star or white dwarf.
D) Cygnus X-1 has pulled matter from its companion star into an accretion disk around itself.
Correct Answer:

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Correct Answer:
Verified
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