Which of these stars (each of which is listed with its apparent magnitude) would NOT be visible to the unaided eye on a clear night?
A) tau Ceti; m = +3.49
B) alpha Centauri B; m = +1.34
C) Barnard's star; m = +9.53
D) 61 Cygni A; m = +5.21

Question

Quizplus · Accepted Answer

Stars with an apparent magnitude greater than +6.0 are generally not visible to the unaided eye under most conditions. Barnard's star, with an apparent magnitude of +9.53, would not be visible without the aid of a telescope.

Which of These Stars (Each of Which Is Listed with Its