Stars Changing Colors or Something Else?

[jferguson]

Hello, two days ago and two days in a row we noticed what appeared to be stars changing colors. Red, blue, green and white. The colors were very clear. It was not a plane. It did not move except for when it disappeared behind the horizon after awhile so I thought it was just due to rotation. Could you tell me what this is? Have you heard or seen this before? If it helps, we live in Gilroy, Ca.

 

[MeteorWayne]

We really need a FAQ on this subject

What you saw was a star (most likely it was Sirius, the brightest in the sky) with it's light being refracted by the atmosphere. Pockets of air between you and the top of the atmosphere act like little prsms, separating the white light into it's component colors. These colors are pointed toward your eye at different times, so it appears to change colors. When the atmosphere is really unstable, it can even appear to blink on and off for a few milliseconds because all the light is bent away from you.

It is easiest to see with Sirius bcause it's so bright, and a certain amount of photons have to hit your eye in order for the cones there to detect color. There are about a dozen stars that are bright enough for the effect to be easily noticed.

It is most easily seen when the star is closer to the horizon, since you are looking through more air. When overhead, there's only about 60 miles of air, when you are looking at a star near the horizon, it can be more than 600 miles of air.

Wayne

 

[squim]

I live in Florida and around 10p in the west I see the same thing, I was curious if anyone knows the name of this star. I thought perhaps it was a plane initially, with all the coloured lights!

 

[origin]

I live in Florida and around 10p in the west I see the same thing, I was curious if anyone knows the name of this star. I thought perhaps it was a plane initially, with all the coloured lights!

It looks like it is sirius in Canis Major.

 

[eburacum45]

Here is a continuous image showing the scintillations of Sirius over time as it moves across the sky; a beautiful image, and very instructive.
http://www.photomeeting.de/astromeeting ... irius1.jpg

 

[origin]

Here is a continuous image showing the scintillations of Sirius over time as it moves across the sky; a beautiful image, and very instructive.
http://www.photomeeting.de/astromeeting ... irius1.jpg

Cool picture!