Intensity of light along the iridium flare

  • Context: Undergrad 
  • Thread starter Thread starter jojotank
  • Start date Start date
  • Tags Tags
    Intensity Light
Click For Summary

Discussion Overview

The discussion revolves around the phenomenon of iridium flares, specifically the intensity of light observed from these flares as they reflect sunlight towards the Earth. Participants explore the reasons behind the gradual appearance and disappearance of the bright spot rather than a momentary flash, considering factors such as the angle of incidence and atmospheric effects.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant notes that the iridium panel acts like a mirror, reflecting light and creating a bright spot that changes in size as the observer's angle changes.
  • Another participant suggests that the sun's non-point-like nature contributes to the changing intensity of the light observed, as different fractions of the panel reflect light at varying angles.
  • There is a mention of the analogy with the penumbra of an eclipse to explain the gradual change in light intensity.
  • A participant expresses a desire for clarification on a light intensity graph, indicating that they are trying to visualize the concept accurately.

Areas of Agreement / Disagreement

Participants generally agree on the factors affecting the intensity of light from iridium flares, but there are multiple perspectives on the specific contributions of the angle of incidence and atmospheric effects. The discussion remains exploratory without a definitive conclusion.

Contextual Notes

Some assumptions about the geometry of light reflection and the observer's position may not be fully articulated. The role of atmospheric scattering is mentioned but not deeply explored.

Who May Find This Useful

This discussion may be useful for individuals interested in optics, astronomy, or the specific mechanics of satellite reflections and their visual effects on Earth.

jojotank
Messages
13
Reaction score
0
Hello.
I have some question about iridium flares. My brains can' t process the whole picture.

Iridium panell works like a mirror and reflects quite some percantege of light to the Earth's surface, where it makes a bright spot with quite a big radeous. An observer sees a bright spot in the sky which is gradually becoming larger and then again slower, until you don t see it anymore. I can t understand why.

Why don' t we see just a momentary flash? Similar to when someone is annoying us with a watch which reflects sunlight into our eyes.

I was thinking that maybe it is because of rotation of the panell. I understand that if the angle of incidence is big, then the intensity will be smaller (changing with cosine function right ?). But then i thought that just a small change in the angle of panell would move this spot far away of the observer's position.

I was also thinking that it may have something to do with atmosphere, scattering of light and all. But i don't believe that would be the case.

My conclusion is that this spot on Earth surface is not of the same intensity - getting smaller towards the edges. But i don' t understand why.

I would be so glad if someone explains it a bit. I can't stand this enigma anymore :)

Thank you so much, and sorry for my english.
 
Astronomy news on Phys.org
One factor (though likely not the only factor) is that the sun is not a point-like light source. As the panel moves into and out of position, a changing fraction of its disc is not reflecting directly to you.
It is the same effect that causes the penumbra of an eclipse.

ole3.gif


penumbraphoto.jpg
 
Like so:

light.png
 
Thank you so much!

I understand it perfectly now. I had some ideas when i was looking at the solar eclipse dark spots on the Earth surface, but i wasn't able to drive it to the end. Thank you so much. I don't want to bi nagging and annoying and i hope you will excuse. Light intensity graph is more like this right?

light.png


Thank you again! I would be smashing my head for a while if you wouldn't help.
 
jojotank said:
Light intensity graph is more like this right?
View attachment 84903
Yes. PhotoShop doesn't do curved lines easily. :wink:
 
Hello Dave, i hope you will be reading this. I just wanted to aks you if this diagram is correct when explaining whole situation. Do you think there should be any corrections?
Thank you :)

internet 2.png
 

Similar threads

Undergrad Light intensity required to shine a light through an opaque object
  • · Replies 22 ·
Replies
22
Views
3K
Undergrad Luminous Fast Blue Optical Transients (LFBOTs)
  • · Replies 0 ·
Replies
0
Views
680
High School My First Iridium Flare - Unexpected Bright Light in the Sky
  • · Replies 6 ·
Replies
6
Views
4K
High School Light and the black matter (Dark Matter)
  • · Replies 2 ·
Replies
2
Views
2K
Undergrad Where can I find publicly accessible data from observatories in Europe?
  • · Replies 5 ·
Replies
5
Views
2K
High School Neutron star 4U 1820-30 spins at 716 revolutions per second
  • · Replies 0 ·
Replies
0
Views
3K
High School Scattering of light in a strange fashion
  • · Replies 2 ·
Replies
2
Views
2K
Undergrad How different is a calcite crystal from a polarizer?
  • · Replies 3 ·
Replies
3
Views
3K
Graduate Drop in intensity when light is focused to a point (telescope mirror)
  • · Replies 8 ·
Replies
8
Views
2K
Intensity of Stars and the Inverse Square Law Problem
  • · Replies 10 ·
Replies
10
Views
3K