Quote:
Originally Posted by renormalised
No...we pass through the spiral arms once every 30-35 million years. As the Sun orbits about the Galaxy (every 250Ma), it bobs up and down with respect to the plane of the Galaxy....roughly +/- 250ly above and below. Right at present, we're about 1-2 million years out and 25ly above the last encounter with a spiral arm...which was in the direction of Centaurus. We're not out of the woods completely, yet. At present we're heading towards what's known as the Aquila-Cygnus Rift, which is a dark, nebula filled region loaded with star formation regions and all sorts of nasty stuff. We won't get there for about 1-1.5 million years. Fortunately, we'll miss the core of the region...just.
The arms themselves travel more slowly than the stars which form in them. If the stars live long enough, they leave the arms to pursue their own orbits about the Galaxy. Most of the stars within a galaxy orbit about it on their own orbits and whilst most orbit roughly in the same direction, their orbits are not all nicely spaced or heading in specifically the same direction. Some orbit the galaxy at high angles, others have almost flat orbits. Some have highly elliptical orbits and others have more or less circular orbits.
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And I thought it was a very simple orbit. Sounds more like the merry-go-round from hell.
I new that the ecliptic plane was
fairly square with the galactic plane but I had no idea how far up and down we went. So we're doing the hoola hoop basically, flying through nasty stuff occasionaly. It's just amazing the earth is still ticking along
relatively unaffected by the sound of it. Well except some measly extinction event now and then wiping 70% of biodiversity. But they were all seafood at the time weren't they? Frogs and snails. That kind of stuff
