Does Arcturus pulse so that it is seen by the visible eye.

[Adhyskonydh]

Complete beginner question. I was viewing Arcturus last night through my telescope and it looked like it was pulsing but I wasnt sure whether that was other influences of say atmosphere or other light interference. I tried to look online but there seems to be a variety of discussions some talking of pulses taking solar days and some talking about regular 1 secong pulsing, but no simple answer to mysimple question.

So simple question, does arcturus pulse so that it can be seen by a casual viewing session.

Thanks

[Tinker1947]

Arcturus is low in the sky in the evening, not getting a reasonable viewing position until midnight so its likely that you were seeing through the haze and therefore seeing it pulse or sometime appear to dance.......

http://en.wikipedia.org/wiki/Arcturus

[Pete Presland]

Its more like twinkling or scintillation than pulsing. As has been said the Earth’s atmosphere disturbs the pinpoint light of a star, especially when just above the horizon so the stars appear to twinkle.

[ronin]

The variation will be from our atmosphere, it tends to be "messy".

Arcturus is a red giant and although they do pulse in the case of Arcturus it is not yet considered red enough for this to have started. Any such feature is presently considered to be too small to be measurable.

Easy way of thinking about it is that no-one is sure, although it is predicted to happen eventually, and with the range of instruments someone would haver measured pulses in brightness a lot more accurate and sensitively then a human eye can detect.

[Perseus_m45]

I have witnessed this many times and I can say its atmospheric . If you want a really good show take a good look at Sirius when its low on the horizon ...It pulses different colors !!!!

mike h

[Tot]

I have witnessed this many times and I can say its atmospheric . If you want a really good show take a good look at Sirius when its low on the horizon ...It pulses different colors !!!!

mike h

Sirius is the best/worst at this - I once spent ages during a night of meteor watching wondering why the police helicopter in the distance wasn't making any noise. It just hovered there, flashing red, white and blue. That was Sirius.

[ghostdance]

Sirius is the best/worst at this - I once spent ages during a night of meteor watching wondering why the police helicopter in the distance wasn't making any noise. It just hovered there, flashing red, white and blue. That was Sirius.

Sirius can be quite a sight can't it?!

I wonder how many times Sirius has got the local branches of the Aetherius Society or the Galactic Brethren out with their thermos's and 'Welcome' signs....?

[jabeoo1]

This topic kind of goes really nicely into the subject of variable stars & the many reasons how stars can appear to fluctuate as seen from earth.  The atmosphere is a good starting point.

Intrinsic reasons such as swelling and expanding as they attempt to grip onto a more stable existence.  The HR diagrams asymptomatic giant branch is also a very interesting phase before the final burn out. 

Extrinsic examples such as binary systems whose orbits sometimes block the lit line of sight are also great topics to connect up to the theme of variable appearances.  

Never fails to make me stop and think this kind of stuff.