Why do stars appear to have different colors?

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Discussion Overview

The discussion revolves around the reasons why stars appear to have different colors, exploring concepts related to stellar color perception, atmospheric effects, and the nature of light emitted by stars. The scope includes observational astronomy and the influence of Earth's atmosphere on color perception.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants suggest that stars emit light across the spectrum, appearing white when viewed from space, but atmospheric effects can alter this perception, making the sun appear yellow or red at different times of day.
  • One participant questions whether a star would appear blue if observed from a distance of a few astronomical units (AU) and speculates about the color perception if the sun were blue.
  • Another participant notes the observable differences in star colors, specifically mentioning the bluish appearance of certain stars and the redder appearance of Betelgeuse when viewed with the naked eye.
  • There is a discussion about the sun's true color being white and how atmospheric scattering affects the perception of its color, particularly during sunrise and sunset.
  • One participant emphasizes that color perception is relative and influenced by the observer's optical system and environmental conditions.

Areas of Agreement / Disagreement

Participants express varying views on the colors of stars and the effects of Earth's atmosphere on color perception. There is no consensus on the exact nature of these effects or the implications for how stars appear under different conditions.

Contextual Notes

Some claims rely on assumptions about atmospheric effects and the nature of light, which may not be universally agreed upon. The discussion includes references to specific stars and their perceived colors, which may vary based on observational conditions.

Who May Find This Useful

This discussion may be of interest to amateur astronomers, students of astronomy, and anyone curious about the visual characteristics of stars and the factors influencing their color perception.

nicedazed
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Obviously if you looked at one it would appear white as it's so bright and stars are black bodies so emit all over the spectrum (correct me if I'm wrong). But as the sun is a yellow star, it looks yellow around it (unless that's the atmosphere of Earth getting rid of blue?) and has a yellow tinge.

If you were placed in space at a distance in the range of a few AU, would it literally appear blue?

If the sun were blue, and Earth's orbit were adjusted so that the new (blue) sun would appear as big as the current (yellow) sun does now, would everything have a blueish tinge?
 
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The direct approach is to go out at night and look at a blue star. There is an obvious difference.
 
Thanks. Both good ideas. I never trust google image searching because perhaps the images are often not true colour. As for looking at stars at night, I'm sure so many of the stars seem to appear bluish, but then again I've never looked up at the sky with a telescope. Having said that, I've definitely noticed Betelgeuse looking redder from the naked eye.
 
Our sun is actually white to our eyes. Yes stars emit in all wavelengths, but they have a peak (actually, I believe our own star has a peak in the green wavelength - but a quick look at the Planck curve explains why we don't see green stars). You are right, it's the effect of the atmosphere removing the bluer wavelegnths from our view of the sun. If you looked up at it during the day, when it is directly above you (i.e. has the least amount of atmosphere to pass through) it would seem white. But we can only really look at the sun when it is rising or setting, that is when it is easiest on our eyes. Nearer the horizon the light from the sun has more atmosphere to travel through before photons register in our eyes, meaning the bluer wavelengths are removed more, so you see it as red/orange. The reason our clouds appear white is because the light from the sun is white If the light from it were primarily purple, we'd have purple clouds!

Stars like Betelgeuse though would appear red to you in the absence of an atmosphere.

Great question though. Colour really is all relative to us because of our optical system.
 

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