Okay, so how's this for something you don't know. There are planets that are not bound to orbit within our universe due to being knocked out of orbit with early development by asteroids and/or another planet. So these planets drift throughout space endlessly and eventually freeze due to a lack of best from a star. If the planet is geothermal like ours and contains water the top of ice can freeze, but the heat of the core can actually keep some water liquid. They can theoretically support life so you can essentially have life on a "dead" planet coasting throughout space.