Talk:Galaxy rotation problem
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"scientists simply assumed that the rotation curve was flat because of the presence of a large amount of matter outside the galaxies"
Are you sure this is correct? How can the presence of matter outside a galaxy affect rotation speeds with?. I thought dark matter was postulated to exist within a galaxy but not all concentrated at the centre as Newtionian models suppose. However I am not confident enough that I am correct to make the change to the page without further research. Watch this space! Theresa knott
- You're right, I'm trying a different wording: "a large amount of matter surrounding the visible part" - At18 21:46 Apr 28, 2003 (UTC)
It would be nice to post the modeled mass distribution in the galaxy that produces the A velocity curve - e.g., don't you need an assumed mass distribution to generate that curve? And wouldn't different assumed mass distributions generate different velocity curves. Is there a mass distribution that it is reasonable or obvious to use to generate the expected velocity curve?
This page is a complete mess. I'm taking a hose to it. -- Decumanus 18:20, 12 Feb 2004 (UTC)
Cleaned up
The page was a disaster. I have cleaned it up. 67.172.158.8 17:23, 24 Dec 2004 (UTC)
Elliptical orbits
One thing that I have never seen is an explanation of the galactic rotation curve that also explicitly takes into account the fact that the spiral arms are not in fact coherent but are a construct of the elliptical orbits of the stars that make them up, as explained by Image:Spiral galaxy arms diagram.png. The implication of this is that a star in a spiral arm is near the aphelion end of the ellipse, and so is going more slowly than a star on a circular orbit at that distance would be. If the ellipses themselves are turning and giving the illusion of the spiral arms rotating evenly, then the discrepancy could disappear. It seems unlikely that this has been overlooked, but I'd be interested to see a discusson that includes this aspect. — PhilHibbs | talk 18:41, 23 Feb 2005 (UTC)
