Why is it that when you look directly at a faint star, you can't see it?

Question

but when you look a little to the side, you can see it clearly?

Answer 1

It has to do with the light sensitivity of the different types of light receptor cells in the eye. There are two types. The cones which see brightness and color are concentrated at the center of the retina. The Rods which are sensitive to low light and contrast (shades of gray) are concentrated at the edges of the retina. By concentrating on your peripheral sight you can just make out the fainter objects in the sky. This is what is called seeing out of the corner of your eye.

Answer 2

The light radiated from a star that we see is what actually was emitted by it many million light years ago!!
That light travels many a million media before we see and is therefore refracted. Thats why stars twinkle(and planets wont, bcoz not many media in betwn Earth and them).
So, some faint stars may be visible only at some angle of incidence(othr than the direct one, bcoz of refraction).

Answer 3

Maybe because the star really isn't in that spot in the sky. Light travels around other objects, so the object is probably blocking the real star, so what you're seeing is just an image, so if you look directly at it, the light is blocked from your vision.

Just a thought though.

Answer 4

peripheral vision is actually stronger than direct vision. this goes back to the first humans on this planet. now we don't need to worry about being attacked by other animals, but back then it was important for survival to be able to see what was happening around us. if a lion was approaching from behind our ancient relatives, the sharp peripheral vision enabled them to be able to see it quickly and hopefully give them more time to run away. now we don't need to worry about being preyed on, but our eyes still have this "feature".