Why are the 'Fixed Stars' so FIXED?

Sure, they're a long way from us...but there are a great many out there in our
galaxy and every object must be in orbit around a mass centre of some kind.

Most do not appear to have moved much in thousands of years.
Should we not expect to see more movement than we do?

....my question may be naive and the answer trivial... so please enlighten me.

"Henri Wilson" HW@.... wrote in message
...
Sure, they're a long way from us...but there are a great many out there in
our
galaxy and every object must be in orbit around a mass centre of some
kind.

Most do not appear to have moved much in thousands of years.

http://schmidling.com/barnard.htm

Should we not expect to see more movement than we do?

How would you go about calculating what to expect? Until
you do that, you can't say whether they move more or less
than expected.

...my question may be naive and the answer trivial... so please enlighten
me.

Bear in mind nearby stars are roughly in the same part of
the galactic disk so tend to share a similar mean motion.
However, your first point is the key one, they really are
a very long way away by everyday standards.

George

In sci.physics.relativity, HW@....(Henri Wilson)
HW@
wrote
on Sat, 03 Feb 2007 22:38:56 GMT
:
Sure, they're a long way from us...but there are a great many out there in our
galaxy and every object must be in orbit around a mass centre of some kind.

Most do not appear to have moved much in thousands of years.
Should we not expect to see more movement than we do?

...my question may be naive and the answer trivial... so please enlighten me.

If one assumes that a star 50 light-years away is moving
at a speed of 2 * 10^-3 c[*], that means it will move
2 light years per millennium. Assuming that it is moving
sideways to us that resolves to about 1/25th of a radian
per millennium, or 2.30 degrees per millennium, or 8.05
arcseconds per year. Even were the star 10x closer (or
5 l-y) one only gets 80.5 arcseconds per year -- or 1'20.5".

Contrast this to Pluto's distance of 39.481 AU or 5.9 * 10^12 m
(semimajor axis), an average orbital speed of 4.666 * 10^3 m/s,
and an orbital period of 248.09 years; this translates into
1.45 degrees per year, despite the fact that Pluto is moving more
slowly (about 1.5 * 10^-4 c) in an absolute sense.

Hence the term applied to the 8 planetei -- Greek for "wanderer".
(Pluto got demoted. :-) )
[*] this is double the estimated speed at which the Sun
is swinging around the Galactic core. It is theoretically
possible for a star to be retrograde.

--
#191,
Is it cheaper to learn Linux, or to hire someone
to fix your Windows problems?

--
Posted via a free Usenet account from http://www.teranews.com

"Henri Wilson" HW@.... wrote in message ...
Sure, they're a long way from us...but there are a great many out there in our
galaxy and every object must be in orbit around a mass centre of some kind.

Most do not appear to have moved much in thousands of years.
Should we not expect to see more movement than we do?

...my question may be naive and the answer trivial... so please enlighten me.


http://reductionism.net.seanic.net/A...nardStar_3.GIF

Barnard's Star was at coordinates 17:57:48.23, +04:42:33.3 (equinox 2000.0) on June 27, 2005.

http://schmidling.com/barnard.htm
Take a long hard look and do the numbers, stop muttering uni****ation, you won't live long enough to see one of them move with binoculars.

On Sat, 3 Feb 2007 17:05:23 -0800, The Ghost In The Machine
wrote:

In sci.physics.relativity, HW@....(Henri Wilson)
HW@
wrote
on Sat, 03 Feb 2007 22:38:56 GMT
:
Sure, they're a long way from us...but there are a great many out there in our
galaxy and every object must be in orbit around a mass centre of some kind.

Most do not appear to have moved much in thousands of years.
Should we not expect to see more movement than we do?

...my question may be naive and the answer trivial... so please enlighten me.

If one assumes that a star 50 light-years away is moving
at a speed of 2 * 10^-3 c[*], that means it will move
2 light years per millennium. Assuming that it is moving
sideways to us that resolves to about 1/25th of a radian
per millennium, or 2.30 degrees per millennium, or 8.05
arcseconds per year. Even were the star 10x closer (or
5 l-y) one only gets 80.5 arcseconds per year -- or 1'20.5".

Yes, thanks for that Ghost. More or less what I thought.

I was wondering why more stars were not seen changing places as they orbit
each other reasonably closely.

I suppose the answer is that all objects in optically resolvable orbits are
always moving very slowly around that orbit.
No large object in our galaxy appears to be moving at anything like c wrt
anything else.....something I find interesting.

Contrast this to Pluto's distance of 39.481 AU or 5.9 * 10^12 m
(semimajor axis), an average orbital speed of 4.666 * 10^3 m/s,
and an orbital period of 248.09 years; this translates into
1.45 degrees per year, despite the fact that Pluto is moving more
slowly (about 1.5 * 10^-4 c) in an absolute sense.

Hence the term applied to the 8 planetei -- Greek for "wanderer".
(Pluto got demoted. :-) )

[*] this is double the estimated speed at which the Sun
is swinging around the Galactic core. It is theoretically
possible for a star to be retrograde.

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

Sure, they're a long way from us...

That's the answer to your question; the so-called "fixed" stars appear
relatively fixed because of their vast distances to us. While light
takes one second to travel to the Moon, 8 minutes to the Sun, one and
a half hour to Saturn and some 5 hours to Neptune, light takes more
than 4 years to travel to the *nearest* star, and hundreds of years or
more to travel to the average star visible to the naked eye in our
skies. That's a big difference!

but there are a great many out there in our galaxy and every object
must be in orbit around a mass centre of some kind.

Indeed true: all the stars we see with the naked eye in our skies
belong to our galaxy, and they are all orbiting the center of our
galaxy with an orbital speed of some 200 to 300 km/s. That's some six
to ten times faster than the orbital speed of the Earth around the
Sun, but the stars are vastly more distant than just some six to ten
times the distance to the Sun. Therefore they appear to move much much
slower.

Most do not appear to have moved much in thousands of years.
Should we not expect to see more movement than we do?

Why should we expect what does not happen?

Mankind saw for many thousands of years that the stars didn't appear
to move much relative to one another, with the exception of 7 bodies
which were called planets (= "wandering stars"): Sun, Moon, Mercury,
Venus, Mars, Jupiter, Saturn. The weekdays were named after the
planets and that's why we have a 7-day week. Now, since mankind had
known for a very long time that this was the case, why should we
"expect" anything different? The reason for this (i.e. the vast
distances to the stars) was found out much later though - ancient man
believed the "fixed" stars were just a little farther away than
Saturn.


...my question may be naive and the answer trivial... so please
enlighten me.

Hopefully done....

--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/

"Paul Schlyter" wrote in message ...
In article ,
Henri Wilson HW@....... wrote:

Sure, they're a long way from us...

That's the answer to your question; the so-called "fixed" stars appear
relatively fixed because of their vast distances to us. While light
takes one second to travel to the Moon, 8 minutes to the Sun, one and
a half hour to Saturn and some 5 hours to Neptune, light takes more
than 4 years to travel to the *nearest* star, and hundreds of years or
more to travel to the average star visible to the naked eye in our
skies. That's a big difference!

but there are a great many out there in our galaxy and every object
must be in orbit around a mass centre of some kind.

Indeed true: all the stars we see with the naked eye in our skies
belong to our galaxy, and they are all orbiting the center of our
galaxy with an orbital speed of some 200 to 300 km/s. That's some six
to ten times faster than the orbital speed of the Earth around the
Sun, but the stars are vastly more distant than just some six to ten
times the distance to the Sun. Therefore they appear to move much much
slower.

Most do not appear to have moved much in thousands of years.
Should we not expect to see more movement than we do?

Why should we expect what does not happen?

Mankind saw for many thousands of years that the stars didn't appear
to move much relative to one another, with the exception of 7 bodies
which were called planets (= "wandering stars"): Sun, Moon, Mercury,
Venus, Mars, Jupiter, Saturn. The weekdays were named after the
planets and that's why we have a 7-day week. Now, since mankind had
known for a very long time that this was the case, why should we
"expect" anything different? The reason for this (i.e. the vast
distances to the stars) was found out much later though - ancient man
believed the "fixed" stars were just a little farther away than
Saturn.


...my question may be naive and the answer trivial... so please
enlighten me.

Hopefully done....


Henri thinks stars are 0.3 LY from us to fit his theory.

On Sun, 04 Feb 2007 22:43:07 GMT, (Paul Schlyter) wrote:

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

Sure, they're a long way from us...

That's the answer to your question; the so-called "fixed" stars appear
relatively fixed because of their vast distances to us. While light
takes one second to travel to the Moon, 8 minutes to the Sun, one and
a half hour to Saturn and some 5 hours to Neptune, light takes more
than 4 years to travel to the *nearest* star, and hundreds of years or
more to travel to the average star visible to the naked eye in our
skies. That's a big difference!

but there are a great many out there in our galaxy and every object
must be in orbit around a mass centre of some kind.

Indeed true: all the stars we see with the naked eye in our skies
belong to our galaxy, and they are all orbiting the center of our
galaxy with an orbital speed of some 200 to 300 km/s. That's some six
to ten times faster than the orbital speed of the Earth around the
Sun, but the stars are vastly more distant than just some six to ten
times the distance to the Sun. Therefore they appear to move much much
slower.

Most do not appear to have moved much in thousands of years.
Should we not expect to see more movement than we do?

Why should we expect what does not happen?

Mankind saw for many thousands of years that the stars didn't appear
to move much relative to one another, with the exception of 7 bodies
which were called planets (= "wandering stars"): Sun, Moon, Mercury,
Venus, Mars, Jupiter, Saturn. The weekdays were named after the
planets and that's why we have a 7-day week. Now, since mankind had
known for a very long time that this was the case, why should we
"expect" anything different? The reason for this (i.e. the vast
distances to the stars) was found out much later though - ancient man
believed the "fixed" stars were just a little farther away than
Saturn.


...my question may be naive and the answer trivial... so please
enlighten me.

Hopefully done....

Yes, I should have worded my question differently.

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

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.

Paul Schlyter wrote:
Indeed true: all the stars we see with the naked eye in our skies
belong to our galaxy, and they are all orbiting the center of our
galaxy with an orbital speed of some 200 to 300 km/s. [...]

And equally importantly, the galaxy is rotating as an approximately
rigid assembly of stars. This makes them appear to move even less.


Tom Roberts

On Sun, 04 Feb 2007 23:02:03 GMT, "Dumbledore_"
wrote:


"Paul Schlyter" wrote in message ...
In article ,
Henri Wilson HW@....... wrote:

Sure, they're a long way from us...

That's the answer to your question; the so-called "fixed" stars appear
relatively fixed because of their vast distances to us. While light
takes one second to travel to the Moon, 8 minutes to the Sun, one and
a half hour to Saturn and some 5 hours to Neptune, light takes more
than 4 years to travel to the *nearest* star, and hundreds of years or
more to travel to the average star visible to the naked eye in our
skies. That's a big difference!

but there are a great many out there in our galaxy and every object
must be in orbit around a mass centre of some kind.

Indeed true: all the stars we see with the naked eye in our skies
belong to our galaxy, and they are all orbiting the center of our
galaxy with an orbital speed of some 200 to 300 km/s. That's some six
to ten times faster than the orbital speed of the Earth around the
Sun, but the stars are vastly more distant than just some six to ten
times the distance to the Sun. Therefore they appear to move much much
slower.

Most do not appear to have moved much in thousands of years.
Should we not expect to see more movement than we do?

Why should we expect what does not happen?

Mankind saw for many thousands of years that the stars didn't appear
to move much relative to one another, with the exception of 7 bodies
which were called planets (= "wandering stars"): Sun, Moon, Mercury,
Venus, Mars, Jupiter, Saturn. The weekdays were named after the
planets and that's why we have a 7-day week. Now, since mankind had
known for a very long time that this was the case, why should we
"expect" anything different? The reason for this (i.e. the vast
distances to the stars) was found out much later though - ancient man
believed the "fixed" stars were just a little farther away than
Saturn.


...my question may be naive and the answer trivial... so please
enlighten me.

Hopefully done....


Henri thinks stars are 0.3 LY from us to fit his theory.

Listen you stupid old dope, stop misrepresenting me or you will end up in
court.
I said that to generate the magnitude changes associated with published
brightness curves, the distance parameter value that has to be fed in is always
less than the hipparcos one. For short period binaries - or whatever they are -
the required distances can be less than 1 LY.

AT NO TIME HAVE I CLAIMED THAT THESE STARS ARE ONLY 0.3 LYS FROM THE ****ING
EARTH.

SO SHOVE IT UP YOUR GLENLIVET BOTTLE.