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Odd star flicker

  1. Nov 21, 2004 #1
    last night i was at the beach with my friends. i was looking up at the sky and i saw a star (two actually) that was flickering between green, red, orange, and the normal white. i have never seen this before it was incredibly weird. at first i thought it was a plane because they have the red and green lights but then i noticed its position was unchanging. does anyone know why this was happening?
     
  2. jcsd
  3. Nov 21, 2004 #2
    It could be a satellite in orbit, and depending on it's angle, the color may change.
     
  4. Nov 21, 2004 #3

    turbo

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    Were the stars really low in the sky? The refractive effects of an unstable atmosphere can be strong, but generally they are the very strongest when the stars are close to the horizon and there is a LOT of air for the light to traverse.
     
  5. Nov 21, 2004 #4
    I know that the moon can be different colors during an eclipse, but the moon is very close to earth, and stars are quite far away.
     
  6. Nov 21, 2004 #5

    turbo

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    The moon reddens during a lunar eclipse because of the light refracted around the Earth's limb. The Earth's atmosphere can produce some pretty dramatic effects, like the "green flash" sometimes seen as the sun is disappearing below the horizon. The reason I asked if the stars were close to the horizon is that the refractive effects of the atmosphere are much stronger when there is a lot of atmosphere for the light to traverse. Stars very high in the sky tend not to "twinkle" very much, since their light comes to us through less atmosphere, and the density differentials in the layers of that atmosphere are more-or-less oriented perpendicular to the light's path. Both of these conditions help to minimize refractive effects.
     
  7. Nov 22, 2004 #6
    the stars were probably between a 30 and 45 degree angle. my friend also noticed it so im not crazy. the twinkling was like that of a normal start twinkling with the white except it would switch between those colors. the next night at my house i saw a star that was twinkling between white and green, possibly red also. i just went outside and there is a star probably 25-30 degrees doing it. its like it is popping between the colors. its quite interesting to watch.

    i also saw a red star but that could be beetlegeuse.
     
  8. Nov 23, 2004 #7

    Phobos

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    Like Turbo-1 said, that color shifting is due to atmospheric effects, which are more pronounced when the star (usually a bright one) appears lower in the sky (more atmosphere to go through than a star directly overhead).
     
  9. Nov 23, 2004 #8
    interesting. has anyone else seen this? its a first for me
     
  10. Nov 23, 2004 #9

    turbo

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    I have seen severe "twinkling" effects including color shifts thousands of times, mostly in stars closer to the horizon. The reasons for this (closer to the horizon) are:
    1) the light from a star close to our horizon has a LOT more atmosphere to tavel through, and atmosphere bends (refracts) light just like the lens of a telescope does. The thicker the "lens" and the denser the "lens" the stronger the bending.
    2) the layers of atmosphere are aligned close to the angle at which the light is coming to us, making small fluctuations in those layers (usually of different densities due to temperature differences) VERY effective in refracting the light. If the light comes to us from a star that is high in the sky (or overhead), the light comes in more-or-less perpendicular to these density boundaries and is refracted to a much lesser extent.
     
  11. Nov 24, 2004 #10

    Nereid

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    Twinkling and colour changes are somewhat subjective ... not only does the external setting make a difference (e.g. how much other light is around, how much glow in the sky, etc), but your own body can lead to quite large perceptive differences (e.g. dark adaption, wind and tears, cold, ghost images from looking at distant bright lights, floaters, sleepiness, and much more). Then there are atmospheric conditions ... in addition to the zenith angle, you have high altitude winds, thin clouds, smoke, haze, and more besides. Many of these can result in big apparent differences in the degree of twinkling and colour shifts, from night to night, even at the same zenith angle for the same star!
     
  12. Nov 24, 2004 #11

    Phobos

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    more info...(thanks to Phil Plait's book "Bad Astronomy")
    Starlight, which is reaching you as a point of light because the source is so far away, is refracted as it enters and passes through the Earth's atmosphere. (Like how a spoon looks bent when you put it in a glass of water.) The Earth's atmosphere is more turbulent further up and there are packets of air called "cells" which move around and alter the amount the light is refracted before reaching your eyes. Different colors of light are refracted by different amounts (e.g., blue & green are more easily refraced than red). As the atmosphere (e.g., cells) are moving around, the amount of refraction changes and the colors you see shift accordingly. (This same refraction is what causes stars to appear like they're twinkling.)
     
  13. Sep 2, 2009 #12
    ok no joke me nd my friend like five minutes ago plus the time it took to set up an account,, saw the 2 stars plus other ones but 2 really stuck out the most nd we dnt know what it is nd we got binoculars nd when we looked a them colsly they stoped blinking nd they were red orange green nd in the very middle a tiny flicker of blue. not a satilight cuz it wuld be in orbit nd moving we watched it for 30 min or more so its nota plane or an ufo its somkind of star. if u find anything else or have questions e-mail us at plowmehard@live.com or myspace us using tht e-mail there is a picture of a fish.
     
  14. Oct 25, 2009 #13
    last night as i was observing i seen a star like described but it was turning red then white over again but when i used my telescope to look at it and it was white so i used my binoculars it was red again
     
  15. Mar 22, 2010 #14
    I saw something like this just now on holiday in adelaide south australia, took some photos as best I could considering conditions as I could not hold the camera very still on full zoom at night. They are on 2 different scene settings.
    [​IMG]
    [​IMG]
    [​IMG]
     
  16. Mar 23, 2010 #15

    I bet it was Sirius. Was it the brightest star in the sky? Sirius is shockingly bright and white and appears to change colors rapidly. Looking at it through my telescope it looked more like a crystal spinning in the light because of all the colors coming off of it.
     
  17. Jun 6, 2010 #16
    yes actually i'm looking at two right now, it's exactly as you describe,I even had my daughter look at it too confirm that I wasn't just seeing things. very unique, awesome sight to see.
     
  18. Jun 7, 2010 #17

    phyzguy

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    I have repeatedly seen the star Antares show this effect, flickering between red and green due to the twinkling of the Earth's atmosphere. Antares is an M type red supergiant with a bright blue-green companion star, and I have wondered whether the change in color has to do with the fact that it is a double star, but I am not certain. For observers in the northern hemisphere, Antares is usually close to the southern horizon, which contributes to this affect, as noted by Turbo-1. Which stars are you seeing show this effect?
     
  19. Jun 10, 2010 #18
    Just also reporting on this. Observing several stars tonight showing this phenomenon.
    Lower angle stars cycle between red,orange,green,blue,and pure white.
    Higher angle stars also flicker more than usual but only cycle between white, blue and green.
    This is observed at low temperatures and high humidity. This conditions may lead to high turbulence in the atmosphere? That could explain the flickering with pockets of more/less dense air bending the light.
     
  20. Sep 7, 2010 #19
    Maybe possible that being right next to ocean had a lot to do with it. The water vapors rising into the cooler night air across the ocean probably agitated the air forcefully, causing the light to refract differently and/or more quickly.
     
  21. Jul 17, 2011 #20
    Hi all, this is my first post on this site. I was lead here trying to google some info on flickering stars. Im in NSW, and tonight it was pointed out to me, a severly flickering "object" in the night sky. Bright white, red, green, blue. As i was watching it, it started to fade away, and it faded away until it was not able to be seen, not even through binoculars. Im wondering if this is what you guys have been talking about as above, or could it be something else? This was observed closer to the horizon, not directly above. Im more intrigued that it disappeared in a matter of seconds.
     
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