Naked Science Forum

General Science => Question of the Week => Topic started by: IzzieC on 01/04/2019 17:03:02

Title: QotW - 19.04.01 - Why do dim stars appear brighter when you look near them?
Post by: IzzieC on 01/04/2019 17:03:02
We received this question from Sean,

"Why is it that when you look directly at small, faint stars they disappear but when you look at a point near them, you can see them?"

Can you help?
Title: Re: QotW - 19.04.01 - Why do dim stars appear brighter when you look near them?
Post by: Colin2B on 01/04/2019 18:15:17
We have two types of light-detecting cells in our retina. Around the centre are cone cells which give us colour vision but need good light levels. Away from the centre are rod cells give us black and white vision but they work better than the cone cells at low light levels. So, looking off to one side allows light from faint objects to strike the rod cells and we see that object.
Title: Re: QotW - 19.04.01 - Why do dim stars appear brighter when you look near them?
Post by: evan_au on 01/04/2019 23:12:06
This is a trick used by astronomers, called "averted vision":
https://en.wikipedia.org/wiki/Averted_vision
Title: Re: QotW - 19.04.01 - Why do dim stars appear brighter when you look near them?
Post by: pensador on 02/04/2019 10:48:20
When sailing at night time, peripheral vision is much better for seeing distant vessels approaching, when you look directly you cant see them. It is also useful in astro navigation for picking out stars. Night vision is lost when looking directly at bright objects, however when red lights are used, instead of white lights you do not lose your night vision so much and can work via a red light and still see in the dark.
Title: Re: QotW - 19.04.01 - Why do dim stars appear brighter when you look near them?
Post by: katieHaylor on 30/04/2019 14:38:10
This question has now been answered, and you can listen to it here - https://www.thenakedscientists.com/podcasts/question-week/how-see-faint-stars (https://www.thenakedscientists.com/podcasts/question-week/how-see-faint-stars)