In a binary star system, one component is found to have about 3 solar masses, the other about 7 solar masses. The 3-solar-mass star is visible from Earth, but the 7-solar-mass star is not. Theoretical considerations declare that the 7-solar-mass star must be a
A) neutron star.
B) cool planetary object.
C) white dwarf.
D) black hole.

Question

Quizplus · Accepted Answer

A 7-solar-mass star not visible from Earth in a binary system, given its mass, is most likely a black hole. Stars with such mass that have ended their life cycle would have undergone supernova explosions, leaving behind dense remnants. Given the mass, it's too heavy to be a neutron star (typically up to about 2.5 solar masses) or a white dwarf (up to about 1.4 solar masses, the Chandrasekhar limit). A cool planetary object wouldn't have such a high mass. Thus, a black hole is the most plausible option, as it is an end state for massive stars and would not emit light, making it invisible from Earth.

In a Binary Star System, One Component Is Found to Have