I Planets or stars that are composed entirely out from Dark Matter.

[MathematicalPhysicist]

Is there a possibility that there are stars and planets that are composed entirely of DM?

How would we detect such stars or planets?
Well, I am not sure about stars, as the definition of a star depends on its fuel that it uses, I guess.

 

[Orodruin]

No. Dark matter has no way of getting rid of enough energy to collapse that far. There is the concept of an early Universe dark star where DM annihilation prevents further collapse. Even these objects are predominantly matter.

 

[MathematicalPhysicist]

No. Dark matter has no way of getting rid of enough energy to collapse that far.

How much energy does it need to get rid of in order to collapse to one of these celestial bodies?

 

[Arman777]

How much energy does it need to get rid of in order to collapse to one of these celestial bodies?

The problem is that DM cannot lose energy. For instance, think two masses (baryonic) that are colliding with each other. If they make an inelastic collision then they will lose some energy which means that kinetic energy of the particles transforms into heat or etc. Now, they are moving as one piece.However if DM is made from particles, according to the observations, they cannot lose their energy via heat. This implies that they cannot combine with each other to create bigger objects. Because this process needs an energy transformation from kinetic energy to heat, which DM particles are not capable of.

 

[MathematicalPhysicist]

However if DM is made from particles, according to the observations, they cannot their energy via heat. This implies that they cannot combine with each other to create bigger objects. Because this process needs an energy transformation from kinetic energy to heat, which DM particles are not capable of.

Contrary to your signature, DM don't connect... :-)