The First Confirmed Black Hole, Cygnus X-1, Was Regarded as Proof

question 53

Multiple Choice

The first confirmed black hole, Cygnus X-1, was regarded as proof that black holes exist because it

• A) is a compact object in a binary system
• B) emits X-rays from a hot accretion disk
• C) is accreting matter from a main-sequence companion
• D) has a period of 5.6 days
• E) has a mass of ten solar masses

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