Happy Solstace

"|-|erc" wrote in message...
...

"Muff Diver" wrote...

So now having brushed against the tropic of cancer the sun is now
headed away from polaris and will turn around after brushing
against the tropic of capricorn and head toward polaris again ?

I always wondered, compared to a fixed point in space, what direction
and at what velocity is the center of mass of the sun, the theoretical
center of mass of our solar system, traveling.

Any astro-whatevers out there know? Or is the planet earth just going nowhere fast.? LOL !

Cross posted to alt.astronomy, the sun orbits the center of our galaxy,
in phase with all the surrounding stars so not like a planets orbit, something
like a 2 million year period if memory serves. galaxy speeds aren't given an absolute
speed in current models, though a relative figure against neighbouring galaxies
might be considered the absolute speed.

Herc

Mensa! Pleasure!

The first thing i noticed was the "center of mass of the Sun" phrase,
which got me to thinking of the complex center due to the pulls of
all the planets and such (e.g., the center of gravity between the Sun
and Jupiter actually lies outside the surface of the Sun). So the Sun
does a bit of a dance in its orbit around the Milky Way.

Then there is the oscillating motion of the Sun and planets in the
Orion Arm of the Galaxy. Scientists believe that the Sun travels
from one side of the Orion Arm to another as it revolves around
the Galaxy's center. Please don't ask for a reference on that one,
as i think i remember reading it in sci.astro once. Maybe true,
maybe not?

As Herc mentioned, the Solar System does revolve around what is
believed to be a black hole at the center of our Milky Way Galaxy.
The period of revolution is from 200 million to 250 million years (i
have read both figures... i think the "250 million" is the more recent
estimate).

In addition, there is the motion of the Milky Way Galaxy around the
center of the cluster called the "Local Group." This includes the
Andromeda Galaxy as well as perhaps over 30 other galaxies, most
of which are dwarf galaxies. There may be more waiting to be
discovered.

Now, the Local Group of galaxies are part of a very much larger
group named the Virgo Supercluster. So there may also be some
presently impossible to measure velocity associated with movement
of the entire Local Group around and/or through this Supercluster.

At this point, it seems that the expansion of space itself begins to
become more and more important. This is believed to have only an
immeasurably tiny effect locally.

You can see that to pick a fixed point in space and then to try and
determine the relative motion of the Sun or anything else to that
fixed point would be a monumental task. And i don't believe it's
ever been done, as at this point in our tek-level it's probably not
possible.

Nice thoughts, though. Thanks for stimulating them.

happy days and...
starry starry nights!

--
Fire... fire in the sky,
'Round we dance till dawn is nigh,
Fire... fire in the sky,
Death is so surreal!

Fire... fire in the sky,
Lovers laugh and lovers cry,
Fire... fire in the sky,
Life is how you feel!

Paine Ellsworth