View Full Version : A New Look at Dark Matter — Is the Milky Way Less of a Behemoth Than Previously Thoug

2014-Oct-13, 07:20 PM
Astronomy is notorious for raising more questions than it answers. Take the observation that the vast majority of matter is invisible. Although astronomers have gathered overwhelming evidence that dark matter makes up roughly 84 percent of the universe’s matter — providing straightforward explanations for the rotation of individual galaxies, the motions of distant galaxy clusters, […]

More... (http://www.universetoday.com/115241/a-new-look-at-dark-matter-is-the-milky-way-less-of-a-behemoth-than-previously-thought/)

2014-Oct-14, 01:44 AM
Shannon, the author, states:

But Rubin found that galaxies rotated nothing like our own Solar System. The outer stars did not rotate slower than the inner stars, but just as fast. There had to be dark matter on the outskirts of every galaxy.

The first two sentences are fine, but I think that third sentence is misleading. There has to be dark matter throughout the galaxy. It happens to extend well beyond the galactic disk, but all that plays little direct part in flattening the rotation curve, which is mainly, if not wholly, due to the mass interior to each star's orbit.

Interesting new finding, or adjustment, though. More accurate measurements are always welcome, especially when the past measurements were apparently not that precise.