The color of stars

[deric]

I was looking early one morning to the southeast about 45deg up. Chicago latitude.  Lots of stars but one was brighter and quite colorful.  It was iridescent or multi colored metallic looking.  Others in the same line of view were just white.  Just wondering what causes this.

[Stu]

Most likely to be atmospheric turbulence affecting the brighter star more than the fainter ones.

Stars themselves range from bluish through white to reddish depending upon their temperature. When they are lower down towards the horizon you are looking through a hundreds of miles of atmosphere and this is what causes the 'twinkling' and multi coloured effect. Sirius is probably the best example for us here, very bright and flashes away madly down near the horizon

Stu

[Special K]

This is a much-loved feature of stargazing that there is a wide spectrum of colors out there to look at.  The Red Giants are particularly appealing, like Betelgeuse in Orion.  As soon as you put any magnification on it, especially binoculars, the color jumps out at you! 

[michael.h.f.wilkinson]

Hard to tell which star it was without any idea of time of year. Sirius can show this effect, but should be lower in the sky.

[ronin]

The normal twinkling and colours are caused by refraction through the atmosphere adn the turbulance in the atmosphere. However there is one bright star that is well known for a range of colours when all others are relatively quiet, that one is Capella.

This is caused by Capella being a double star where the 2 components are very close and quite similar but not the same. So what you see is "one" star but the colour spectrum from 2. When this comes through the atmosphere you do get a bigger range of colours hitting the eye.

[Merlin]

We can get a better assessment of a star's colour by making it alittle out of focus, so that it appears as a disc.