Twinkling stars?

Hi all,

ya know when a star twinkles is that an actual explosion or chemical reaction? An if it is isit as light years would have it the star exploding a long time ago an its only now we see it??

Stars don't actually twinkle -- only our atmosphere makes it look that way. Within the atmosphere between you and the star there are pockets of air at slightly different temperatures. These cause the light from the star to deflect slightly as it crosses the boundaries between different-temperature pockets. As the air moves about, the pockets you're viewing through change and the star appears to twinkle.

This effect (the air pockets) is also what is referred to astronomically as the "seeing". Good seeing means either the air is very uniform in temperature, or the pockets are very large. In either case, they don't smear the image in the telescope as much (or make it jump around in smaller scopes).

Cheers,
-- Jeff.

I think that the twinkling we see here is purely a result of the turbulence and differing temperatures in the atmosphere. If you look at a slightly twinkling star through binoculars it no longer is seen to twinkle. Stars closer to the horizon twinkle more because you are looking through more of our atmosphere.
I find amount of "twinkle" to be a good indicator of how poor the seeing will be on that particular night.

Would atmospheric pressure then have an effect such as QFE? also would it be a good judge so if stars where not twinkling that it would mean good observing conditions

QFE:pressure at sea level

I'm much less clear on this one, but as I understand it a twinkling star is a good indicator of poor seeing conditions, but a non-twinkling star is not necessarily an indication of good seeing conditions.

I've never heard and explaination of why though....

-- Jeff.

Thanks jeff