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**Henri Wilson** · February 5th 07, 10:04 AM posted to sci.physics.relativity,sci.astro

On Mon, 05 Feb 2007 08:12:11 GMT, (Paul Schlyter) wrote:

In article ,
Henri Wilson HW@....... wrote:

I was really wondering about well separated binary pairs...why they weren't
seen to be changing places more frequently...but again 'distance' probably
provides the answer.
I know some such binaries are recorded,

...not only "some" - it's actually a quite large number of binaries
which have had their orbital motion measured and their orbits
determined. Thousands of binaries have had their orbits
determined..... btw the first person who measured orbital motions of
binary stars was William Herschel, several centuries ago.

Paul, I thank you for your very good comments but since I don't post to
sci.astro very often, I should warn you that am a proponent of the ballistic
theory of light.
I say that light in space moves at c wrt its source star and that most
astronomers are under a delusion in believing that is it moves at c wrt Earth.

but generally, those in resolvable orbits will be moving very slowly around
their orbits.

It seems you have a quite small telescope. Of course whether a binary is
resolvable depends a lot on your telescope: larger scopes will be able
to resolve many more binary stars.

I don't have a telescope at present...just read what others have to say..

However, for very heavy stars, the orbit period at say 0.01 LY radius could
conceivably be less than one hundred years....and movement should be
observable.

If you want to observe orbital motions in binary stars most easily, you should
pay attention to nearby binary stars.

Alfa Centauri, our most nearby star system at some 4.2 LY distance,
will show considerable orbital motion during a human lifetime (its
orbital period is some 80 years). But it's too far south for most
northern hemisphere observers to see.

I'm OZ. We have a great view of the Milky Way. On clear nights I can see the
whole spiral formation.

I have myself seen orbital motion in two binaries, with causal visual
observation:

70 Ophiuchi: near its perihelion in the 1980's I observed and drew
this binary once a year. After only some 4-5 years it had changed its
PA by some 90 degrees. Now it's away from perihelion and therefore
moving more slowly, but keep an eye on this pair anyway and you'll see
orbital motion. Although now it may take a decade or two. IF you
attach a micrometer to your eyepiece, so you can detect smaller
changes in PA or separation, you'll detect the motion sooner of
course.

Were you able to resolve the orbit parameters....eccentricity, yaw?

Gamma Virginis: In my youth in the 1960's, this binary was easily
resolvable with a separation of some 6 arc seconds. Today it's near
perihelion, with a separation of a fraction of an arc seconds and
most telescopes will be unable to resolve it. Within several years
the pair will widen again, making Gamma Virginis resolvable also
with smaller telescopes.

Thanks for that.

I should advise you that for some time, I have been studying variable star
light curves with the aim of proving Einstein wrong...which of course he was.

Light from distant stars travels at c wrt those stars and at c+v wrt planet
Earth.

Binary stars in orbit, emit light at sinusoidially varying speed wrt Earth.
Their 'fast' light catches the slower light, causing 'bunching', which appears
to us as a variation in brightness.