changing colour star?!! Help!

[cheb]

Hi, i was wondering if anyone could help identify the star i spotted tonight, i would say it was capella or very near to capella at 23.25 tonight NNW literally just off North to the west, low in the sky. It was changing colour rapidly between Red, Blue, Green and Purple, when i took the scope slightly out of focus it was amazing to watch, like a collidoscopeing jellyfish!

As i said im guessing it was capella from looking at stellarium, but i have never seen the colour changing before, is it because its low so there might be low cloud interfearing, and with the main changes of colour being R.G.B im kind of guessing it is something happening with the light coming in the atmosphere??

Any help or ideas?

[rowan46]

thats right light refracts as it comes trough the atmosphere the lower the object the greater the refraction as it has more atmosphere to go through the change in colour was caused by the turbulent air currents changing atmospheric density and hence the colouring of the objects as its angle of refraction was changed ( I think, although that maybe something I have just made up)

[alanjgreen]

Maybe "Adhil" - I had the same thoughts when I bumped into it 2 weeks back

[michael.h.f.wilkinson]

Stars low in the sky get a "disco-ball" appearance due to atmospheric refraction and turbulence. This is one of the main reasons Sirius B is so very hard from our latitudes.

[cheb]

thanks for the replys, it just stood out so much and i know i have never seen it so bright before. Flashing thoughts of being about to see a supernova and such then sense prevailed!!

[Hals]

Flashing thoughts of being about to see a supernova and such then sense prevailed!!

I think we've all had that moment at least once !!

[ronin]

It will be Capella it is well known for the assorted colours.

The "cause" is atmospheric refraction which causes the colours to seperate, the multiple colours are caused because Capella is a considered a "double" star and they are fairly similar with a slight colour temp difference. In reality it is a 4 star system but the other 2 are dim cool red stars and a fair distance off. The main 2 are big and in close orbit to each other. Hence we see them as 1 star at this distance.

So what you get is refraction of 2 stars which have a slightly different colour to each other. So there are more colours to play with and split and come through. Makes for an entertaining star to observe.