Author, Andy Lloyd, demonstrates in his book (and now in the Kindle version), The Dark Star, that a planet beyond Pluto need not be cold and lifeless! He says that astronomers know this. This is not controversial for them. They understand what brown dwarfs are, and they realize that these brown dwarfs provide enough heat and light to provide habitable environments on planets orbiting these failed stars.
Lloyd says that one might well be circling the sun, in the comet clouds that make up the bulk of the solar system’s volume.
Originally published in 2005, the book recognizes the difficulties that detecting such a body present – however, Lloyd puts forth a convincing argument with over 220 pages pages of research, 39 pictures and graphics, many in color and not in the original hard copy book. There are hundreds of scientific references that offer compelling evidence for the existence of Planet X!