The smallest angle in the sky that can be resolved from Earth's surface, using the best telescopes under the best observing conditions, is approximately 0.1 arcsec. (You may wish to review the small-angle formula in Box 1-1 of Universe, 11th ed.) The smallest feature that can be resolved at the distance of Neptune is therefore approximately:
A)1/2 of the diameter of Neptune.
B)1/200 of the diameter of Neptune.
C)20 times the diameter of Neptune.
D)1/20 of the diameter of Neptune.

Question

Quizplus · Accepted Answer

The smallest feature that can be resolved at the distance of Neptune is approximately 1/20 of the diameter of Neptune. This is because the smallest angle that can be resolved from Earth's surface is 0.1 arcsec, and the distance to Neptune is approximately 30 AU. Therefore, the smallest feature that can be resolved at the distance of Neptune is approximately 0.1 arcsec * 30 AU = 3 AU, which is approximately 1/20 of the diameter of Neptune.

The Smallest Angle in the Sky That Can Be Resolved