[CraigS]

Love to start this thread with Robh's gem from a few days ago ..

Originally Posted by Robh

But just how much more complicated are things going to get? If dark energy exists, its nature is going to be even more elusive than dark matter.

and now comes Dark Matter planets !! …
Dark matter could provide heat for starless planets

In a resent paper posted at arXiv.org and submitted to Astrophysical Journal, Dan Hooper and Jason Steffen, physicists at Fermilab in Illinois, present the theory that cold and dark planets, not heated by a star, could be heated by dark matter. In theory, this dark matter could produce habitable planets outside of what is known as a habitable zone.
…
Hooper and Steffen suggest that should this dark matter be trapped within a planet’s gravity, the bursts of energy could produce enough to warm the planet. When it comes to Earth, the energy that could be produced is low, but in areas of space where there are high densities of black matter; Hooper and Steffen believe there is the possibility of finding planets that could be warmed in this way.

And so … do we really know what we're looking for .. and where ?
What is a habitable zone ?

Cheers