Why is it that dim stars in the night sky sometimes disappear when you look directly at them?

Question

Quizplus · Accepted Answer

The light from dim stars is focused on the cones in the fovea when you look directly at them. Cones are less sensitive to light than rods, which are more peripheral in the retina and better at detecting low light levels. This is why dim stars can disappear from view when looked at directly, as the area of the retina with the highest concentration of cones (the fovea) is not as effective at detecting low light.

Why Is It That Dim Stars in the Night Sky