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  1. #1
    Sophro's Avatar
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    Default Strange Flashing on Sirius



    Hi all!

    On Friday night at approx. 22:45 GMT, my friend and I were out when he asked me what the bright light in the sky flashing red and blue was. From my time stargazing I knew immediately that it was Sirius (confirmed by its position in relation to the Orion Constellation). He remained adamant that it couldn't be a star as it was flashing red.

    If I wasn't 100% confident that it was Sirius, then I to would not have believed it to be a star due to the erratic flashing. This is the point of my post: why on earth was it flashing these colours? (and I do realise that it often has a blueish tinge to it, but in all my time stargazing I have never seen any red). I kept track of it during the 20 minute journey, during which the colour flashing continued. My original reaction was that maybe it has something to do with light refraction, but I don't think it was low enough on the horizon at that time (although I haven't yet been able to confirm this on Stellarium).

    Has anybody got any thoughts on the matter?

    Thanks,

    Seán

  2. #2
    EricFD's Avatar
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    It sounds like some kind of atmospheric refraction--or more correctly 'diffraction'. Many times ice crystals in the upper atmosphere can cause the light from stars to be diffracted in the same way a prism or diffraction grating splits visible light into spectral colors.

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  4. #3
    Dublin sky watch's Avatar
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    Default

    I have seen that many times over here as well. But usually Sirius is away to my south which is overlooking Dublin city. So even high up from the horizon (40") it still flashes all sorts of color. I put it down to the pollutants in the atmosphere from the traffic. But it always gets phone calls regarding ufo sightings.
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    When the seeing is really poor -- usually meaning there's a lot of atmospheric turbulence -- it's not uncommon to see bright stars go through apparent color changes. At some moments the atmosphere will be refracting the light such that you see more red, at other moments you see blue because the red light is being refracted away from you.

    Either that, or else the red flashes were the Vogons' targeting lasers...

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  8. #5
    Olon the Astronomer's Avatar
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    I saw sirius flashing colors too, but if it is atmospheric turbulence, why aren't the other stars flashing too?

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    Sophro's Avatar
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    Cheers for the replies guys!

    Olon: I can only assume that Sirius flashes so vigorously because of the fact that it is much brighter than other stars!

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    Default Wth

    I saw Sirius flashing last night as well(12-31-2010) I noticed it at 8:30 pm PST and it was still flashing when I went to bed at 3 am. I will be looking tonight and hoping it is as incredible as it was last night. Unfortunatley I did not have a telescope available. The other stars in Orion etc. were not flashing erratically, so I doubt it was atmospheric interference from our side. One friend hypothyesized it could be a gamma ray burst from the dog-stars, but I am too new to astronomy to be able to say that with any certainty. Please keep your eyes open tonight and try to help me understand what I saw. It was so pronounced that I thoughtit was a Chrtistmas light in a tree at first.

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    Default Sirius flashing

    I saw it tonight around 8 pm EST through my LS-6" scope with medium magnification. Flashing like a strobe light...Through the scope it looked almost like the top of the star was flashing blue to green while the bottom was flashing a red to orange color. Its beautiful to see, but sure enough seeing was not all that great, but no other stars were acting up near like that.

    It was doing the same thing last night...maybe even worse, but I did look at it a bit earlier last night. It does seem to calm down a bit as it rises, but was well above the horizon both nights and producing a great show.

    BillE

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    Default

    Last night (1/4/2011) Tues, a friend and I were stargazing, and Sirius came right over the house. It was very bright, and flashing colors. Now, around 10:00 / 10:30 PM, it was still "fairly" close to the horizon, so, I'm thinking atmospheric conditions.
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    Any star that is relatively close to the horizon will flash different colors. If you look at other stars I am pretty sure they will have crazy flashing as well. Another optical effect is stars appearing to move around. I watched Spica one night and if I hadn't known better I would have sworn it was an alien spaceship with the way it was flashing colors, blue, white, yellow and red along with its "apparent" motion.
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