Multi-colored Stars

  1. I was out observing about an hour ago (finally found M51 for the first time :biggrin:) when I noticed what I assumed was a star to the northeast just a few degrees above the horizon. I looked at it and immediately noticed it appeared to be flashing, but not like an airplane. I stared at it more closely and saw that it looked red, green and blue, and that it was changing colors. Looking at it through my finder scope and then my telescope at low magnification it looked like all three colors at once, but looking at it at much higher (250x) magnification it looked like all three colors at once with a halo around it that was changing brightness every half second or so and sometimes disappearing altogether. There was another star doing this too, but it was higher up in the sky.

    The only theory I can come up with for this is that we got rain yesterday, and some of it could still be lingering in the atmosphere. The starlight could be getting "split" (I'm not sure of the correct term, diffracted?) into rainbowy colors. This would make sense for the low star near the horizon because the light would be traveling through the atmosphere farther to reach me than if it was closer to the zenith, but it doesn't explain the other star that was much higher up.

    Any ideas or explanations for this? Thanks in advance.
     
  2. jcsd
  3. DaveC426913

    DaveC426913 16,439
    Gold Member

    The term you're looking for is scintillation. It is caused by perturbations in the air from warm/cold differentials in the column of air through which you are looking. In stable air of a uniform temperature, this effect is greatly reduced.
     
    Last edited: Apr 14, 2008
  4. Last night was much colder than it had been during the day and I didn't allow as much time as I usually do for the scope to cool off so that would make sense. Thanks for the reply.
     
  5. russ_watters

    Staff: Mentor

    Scintillation makes stars twinkle. What makes them twinkle in color when they are low is the refraction of the atmosphere separating the colors like a prism.
     
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