About light -- why when I look at a star I see rays around it?

[CollinsArg]

Hi! I'm not studying physics and what I know about light is mostly what I've read on the internet and what I've learn thinking and observing the nature.
I come to realize that the space is full of light. When I look at the black space, I don't see light but I know that is light everywhere up there, I don't see it because there isn't anything that stands and blocks the light so that it can bounce and come to me, but it is there. My question is, why when I look at a star I see rays around it? it suposse that light must be something behind making contrast so that light is reflected. what is explanation and an photonic level?. (sorry for my grammar I'm speak Spanish).

Thank you

 

[Burner1234]

You see rays around a star because the light you see comes directly from the star without any obstacle in between and when it enters the Earth's atmosphere it undergoes continuos refraction by the atmosphere's increasing density, when it reaches your eye you can see the star but atmospheric density is not constant so the light cannot reach you continuously ,instead it keeps on changing its position due to changing density of air at different junctions of atmosphere so you see the star twinkling the rays around it are just the scattering of light done by dust particles which are near your eye.

 

[Drakkith]

My question is, why when I look at a star I see rays around it?

The light is scattered by inconsistencies and aberrations in the atmosphere and your eye.

 

[jbriggs444]

https://en.wikipedia.org/wiki/Diffraction_spike

 

[davenn]

https://en.wikipedia.org/wiki/Diffraction_spike

but he didn't indicate he was using a scope ... tho that thought crossed my mind

why when I look at a star I see rays around it?

@CollinsArg please clarify if you were using a Newtonian scope or directly looking at the stars with no optical helpDave

 

[HallsofIvy]

This could also be the result of a slight astigmatism.

 

[pixel]

My question is, why when I look at a star I see rays around it?

Do you have astigmatism?

 

[CollinsArg]

but he didn't indicate he was using a scope ... tho that thought crossed my mind
@CollinsArg please clarify if you were using a Newtonian scope or directly looking at the stars with no optical helpDave

Without scope. What I mean is, suppose that I'm looking at Jupiter, it looks like a bright big star, but Jupiter is a round planet, but I don't see the light round, I see it almost like the tipical symbol of a star.

 

[CollinsArg]

Do you have astigmatism?

Nope, I don't

 

[jbriggs444]

If you tilt your head while viewing Jupiter do the rays rotate with your head or stay fixed?

 

[glappkaeft]

Without scope. What I mean is, suppose that I'm looking at Jupiter, it looks like a bright big star, but Jupiter is a round planet, but I don't see the light round, I see it almost like the tipical symbol of a star.

All the planets (although just barley in the case of Venus at close approach) are smaller than the resolution of the eye and therefore appear point like. The most mundane effect of their larger angular diameter noticeable using the naked eye is that they tend to twinkle less than stars.

 

[davenn]

Without scope. What I mean is, suppose that I'm looking at Jupiter, it looks like a bright big star, but Jupiter is a round planet, but I don't see the light round, I see it almost like the tipical symbol of a star.

stars and planets should look pinpoint to the naked eye, UNLESS you have an eye problem
you shouldn't be seeing any spikes from the stars

 

[CollinsArg]

stars and planets should look pinpoint to the naked eye, UNLESS you have an eye problem
you shouldn't be seeing any spikes from the stars

Mmm, that's weird: So you see stars like this?:

What I see is most like this:

 

[CollinsArg]

If you tilt your head while viewing Jupiter do the rays rotate with your head or stay fixed?

nice, I'll try that!

 

[davenn]

Mmm, that's weird: So you see stars like this?:

What I see is most like this:

yes, I and I would suspect most people see stars as in the top pic

The diffraction spikes you see in that bottom image are what you get when using (more accurately) photographing with a Newtonian telescope

eg...

You don't get them with Cassegrain or Schmidt-Cassegrain telescopes because the secondary mirror doesn't have a spider to support itDave

 

[sophiecentaur]

All the planets (although just barley in the case of Venus at close approach) are smaller than the resolution of the eye and therefore appear point like.

I don't have 'Elf' vision but, when I look at Jupiter, it looks definitely like a disc. Likewise for Saturn - but only just. Mars definitely looks different enough to convince me it's also a disc. It's not just the 'un-star-like' appearance, I'm sure.
Venus, of course, really does look like a little Moon and you can even see its phases.

 

[davenn]

I don't have 'Elf' vision but, when I look at Jupiter, it looks definitely like a disc. Likewise for Saturn - but only just.

Naked eye ?

Have never ever heard anyone else say they can make out discs of those planets naked eyeDave

 

[Vanadium 50]

I wouldn't say I can see the disk of Venus, but I definitely see a difference in shape from its phases - it looks rounder or longer depending on time of year.

 

[jack476]

I don't have 'Elf' vision but, when I look at Jupiter, it looks definitely like a disc. Likewise for Saturn - but only just. Mars definitely looks different enough to convince me it's also a disc. It's not just the 'un-star-like' appearance, I'm sure.
Venus, of course, really does look like a little Moon and you can even see its phases.

Naked eye ?

Have never ever heard anyone else say they can make out discs of those planets naked eyeDave

My guess is that it's probably just a halo he's seeing around the planet when he looks at it in the night sky.

Which is a sign he should think about vision screening, by the way.

 

[sophiecentaur]

Which is a sign he should think about vision screening, by the way

Last month I had a sight test for new specs and I could read the bottom line, as usual (with the new prescription, of course). The appearance of Jupiter is so strikingly different from the stars and the only quality that I can recognise is its Moon-like appearance. You can keep your Rayleigh Criterion and your Airey Discs (which are only rules of thumb). My subjective appreciation of those planets is that they are tiny discs. This, of course, could be because I have learned what they are but I could guarantee, if someone placed an equivalent image somewhere else, I would 'see' the same thing. Not keeping up with the published tables of ephemera or knowing the star maps I still see what I see and , when checking on the web, I am nearly always right. I try to be as objective as I can be. Could it just be the lack of twinkle? Perhaps.

 

[phinds]

I agree w/ Sophiecentaur. Last summer, I think it was, two planets, Jupiter and Venus I think, were in the sky fairly close together on a very clear night when the university next door was closed and there was relatively little light pollution. I was struck by the fact that one of them (Jupiter, I assumed) was clearly a little bitty disk and the other was pretty much point-like although brighter than the other stars.