Astrophysics - star color index

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Homework Help Overview

The discussion revolves around the apparent color of a star that emits uniform intensity across all visible wavelengths, focusing on how this might be perceived from Earth's surface.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants explore the implications of a star emitting equal intensity across the visible spectrum, questioning whether the perceived color would be white or black. They discuss the role of atmospheric effects and the nature of light perception.

Discussion Status

There is an active exploration of ideas, with participants questioning assumptions about color perception and the influence of the atmosphere. Some guidance is offered regarding the relationship between light intensity and color perception, but no consensus has been reached.

Contextual Notes

Participants note the complexity of the problem and the potential for atmospheric scattering to affect the observed color of the star. There is also mention of the star's brightness relative to the Sun and the implications for visibility.

hfenton
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Homework Statement



If a star emits the same intensity of radiation at all visible wavelengths, what will be its
apparent color at the Earth’s surface?

Homework Equations



No equations...

The Attempt at a Solution



I realize that a horizontal line would occur through the visible spectrum if a curve was plotted on an intensity/wavelength diagram, however, considering there is no true peak in the visible colors, I have no idea what color is likely to be seen. I have thought that it might be white or black, but am not really confident with those answers. any help would be appreciated.
 
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Because human eyes are sensitive only to the visible spectrum, so narrow it down :wink:
As you deduce, there are only 2 possible cases: white or black. When is a thing black to our eyes?
 
we see black when light is not present. therefore, would this star have to be pure white? Then, because I am seeing it from Earth's surface, should I take into account the effects our atmosphere has on light, such as scattering? I think I am making this problem more difficult than it is.
 
I also think you're making it more complicated than expected, but making problems complicated is crucial for reasoning :biggrin: Fortunately you're right in this case I think.
Have a look at this: http://en.wikipedia.org/wiki/Diffuse_sky_radiation. I suppose that we don't have to gaze at the Sun :biggrin: so the intensity of light from the star here is small (we know that stars except the Sun are not so bright when observing from the Earth), i.e. we have to look directly to it. Since the shorter wavelength radiation is easier to be scattered by the atmosphere, what we receive if looking directly to the star is more of longer wavelength radiation.
Anyway I'm no expert, so don't rely on my thought :biggrin: Justify it yourself :wink:
 

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