Episode Eight : Gliese 851 g
In the podcast the question arose as to why they thought this planet was tidally locked and, more to the point, how they could know this.
It turns out that it's not that they know it to be the case, more that they suspect it to be the case.
Gliese 851 is old. Really fraking old. Somewhere between 7-11Gy. The best models that we have at the moment would have any planet that close to it's parent star more likely to be tidally locked to the parent than not. The reason for this is that planets tend to not be perfect spheres and the various torques acting on a planet over that amount of time would have allowed the various forces in play to have balanced out.
Just in case you were wondering. ;)