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Does dark matter not produce heat or radiation after a collision etc?
Or, we detect radiations having no generators?

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As I understand it there aren't really "bodies made up of dark matter", because being very weakly interacting it has no way to shed relative momentum and collecting into a "body". Instead you get widely dispersed gasses. – dmckee Oct 17 '11 at 7:54
A sort-of DM objects, "Dark Matter Stars", are theorized to have existed in the early Universe. They'd consist of part DM, part normal matter, but the DM would be so dense that DM particles would frequently collide and, assuming DM is its own antiparticle, annihilation would happen and release EM radiation which would heat up the ordinary matter in the dense clouds, preventing them from collapsing into normal stars. These DM stars would be clouds of maybe a few thousand AUs extent, glowing in the infrared but not in optical light. – Thriveth Dec 15 '13 at 0:25
up vote 8 down vote accepted

It appears Dark Matter (DM) does not radiate any electromagnetic radiation, hence the 'Dark' part of the name. It does however appear to collect together due to gravity, hence the 'Matter' part. It appears to only very weakly interact with other types of matter during 'collisions' and therefore has no method of shedding momentum or energy in a collsion and does not therefore collapse as ordinary matter will under gravity.

The Bullet cluster is a great example of two amounts of DM passing through each other while the ordinary matter collides and is left in the middle.

The exact nature of DM is purely speculative at this moment in time; ATLAS at the LHC hopes to find particles that would fit the bill (supersymmetric neutrinos) but has yet to find any proof of these.

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Aside: There are at least half a dozen "direct dark matter" experiments either running or building right now, and these are based on some very general assumptions about the physics that applies. The collider experiments get there under a more restrictive set of physics assumptions. – dmckee Oct 17 '11 at 15:05

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