With regard to the interview with Catherine Haymans [NAKED SCIENTISTS, 4TH JULY 2013], she said if you counted the visible stars in the galaxy, the implied mass was not enough to account for the speed of the stars around the center of the galaxy. She did not mention invisible stars (black holes and neutron stars and brown dwarfs) which might be orbiting but not visible?
Dominic - Yes, heís basically right and we did have to move very fast in that interview because dark matter is a vast subject. There are whole books written about the topic, but Catherine was saying, there was clearly something in our galaxy that has a lot of mass to it, but that we can't see that isnít producing the light. Now, in the past, people have thought that could be failed stars, that could be black holes, but if it was in the form of compact objects like that you'd expect those objects from time to time to pass in front of stars in the night sky. And thatís actually detectable phenomenon. Itís called microlensing and there are surveys looking for it. And while we have seen that phenomenon happening, itís quite rare. That tells us the number of those compact bodies is quite small. So, most of these mass must be in another form which we think is quite diffused and thatís these WIMPs that Catherine talked about. We donít know what they are, but thatís what Catherine is going after to identify.
Chris - WIMPs.
Dominic - Weakly interacting massive particles.