February 06, 2006

Dark Matter Temperature Measurement

BBC News science reporter Jonathan Amos interviews (February 5, 2006, 23:25 GMT) Gerry Gilmore, IoA, Cambridge, on first measurements of properties of dark matter:

"It looks like you cannot ever pack it smaller than about 300 parsecs - 1,000 light-years; this stuff will not let you. That tells you a speed actually - about 9km/s - at which the dark matter particles are moving because they are moving too fast to be compressed into a smaller scale."

"The speed is a big surprise. Current theory had predicted dark matter particles would be extremely cold, moving at a few millimetres per second; but these observations prove the particles must actually be quite warm (in cosmic terms) at 10,000 degrees."