Galactic Evidence for Dark Matter
Most recent answer: 06/08/2014
- Wouter (age 24)
Netherlands
Dear Wouter,
Your question makes sense if the hypothesized dark matter has the same radial distribution as the ordinary matter in a galaxy. However if the dark matter particles do not have electromagnetic or strong interactions and only interact weakly through the electro-weak force and gravity then their galactic radial distribution doesn't have to be the same as ordinary matter. Their gravitational interaction would, however, affect the radial-orbital velocity distibution of ordinary stars. See:
These particles are sometimes called WIMPs for Weakly Interacting Massive Particles and would interact only via the electroweak and gravitational force. See . Many experiments are underway worldwide searching for these particles. See .
So far no stong evidence has shown up. Stay tuned.
LeeH
p.s. The sorts of pulls from nearby stars that you ask about would give motions in all different directions as the stars circled about their neighbors. The motions that suggest dark matter are more systematic, part of the overall rotation of the whole galaxy, not just little swirls here and there. Mike W.
(published on 06/08/2014)