Kmurphy22

I have lately been pondering the possibility of life existing on a planet that does not have a sun. So far the little research I've done has suggested that the core would have to be hot enough, coupled with a much thicker atmosphere in order to hold an appropriate temperature to sustain life. Other than that I'm pretty stuck. What would be the parameters of such a core and/or atmosphere? Also, the biggest mystery to me is how plant life would be able to thrive, or if life could possibly thrive without plants at all (probably a topic for a different thread). Any information would be much appreciated. Thank you!