A Red Giant Star Is Found to Be Orbiting an Unseen

question 13

Multiple Choice

A red giant star is found to be orbiting an unseen object with a short orbital period. By measuring the speed at which it orbits, astronomers deduce that the object has a mass of 10M _$\odot$ This object is probably a __________ because __________.

• A) black hole; the giant star is massive and could only be in orbit about something even more massive
• B) black hole; its mass is too large to be a neutron star or a white dwarf
• C) neutron star; any supernova that would have made a black hole would have destroyed the red giant
• D) M-dwarf star; only such stars would be faint enough to go unseen in this system
• E) black hole; most red giants orbit neutron stars, and neutron stars can turn into black holes

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