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Labguy
#7
Nov28-03, 01:24 PM
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Originally posted by Nereid
AFAIK, the motion isn't a simple ellipse.

For example, there is a 'vertical' oscillation, about the mid-plane of the disk. I don't remember what the period of this oscillation is, but it's unlikely to be a simple fraction of the rotation period. The amplitude is modest, only a few tens of parsecs, IIRC.

Then there are encounters with giant molecular clouds, which don't necessarily orbit the centre of the galaxy in the same way the Sun does.

Lately nearby galaxies in the process of being canabalised by the Milky Way have been discovered (Saggitarius, Carina); the extent to which they affect the orbit of the Sun is, as yet, unknown.
There are a bunch of interactions (pertubations) as you say, but most sites quote a 225 to 250 million year "orbit" for our solar system around the galaxy. That's a long time, but still very short on the time scale of galactic collisions.

http://www.chron.com/content/interac...ds/990602.html
states 226 million years.

Labguy