Solitary celestial body with support for humanoid life
Suppose that a god has created a universe with nothing in it, except for a single, solitary celestial body. For simplicity, I'll call it a planet, although it most probably technically won't be. For instance, it isn't orbiting anything, because there's nothing to orbit in this particular universe.
Would it be possible for that planet to support sustainable humanoid life?
I was also wondering what the observable effects are of a profound lack of matter in the universe. For example, would it matter for an observer on or below the surface of the planet that there is no cosmic radiation (assuming that there is, indeed, none)?
Some story-specific elements that may be taken into account when considering an answer to this question are as follows:
* The god can engineer the planet any way he likes, but he prefers to mass produce as much as possible. For example, the Death Star from Star Wars would technically suffice as a habitable planet/moon/space station, but the sheer amount of electrical engineering involved alone would drive the god crazy. Think of it this way, if the god had to make a thousand universes similar to this one, he wouldn't choose a design that requires an inordinate amount of attention to details. Sure, he's immortal, but not immune to tedium.
* The god may do some maintenance work every now and then. For example, it may replenish an energy source used to heat to planet. This shouldn't have to happen very often. 258
More than once every 1000 years is too much work.
* The humanoids that will inhabit the planet resemble humans, but they may have been redesigned in subtle ways to take into account the living conditions on the planet. For example, certain chemicals that necessarily appear in the atmosphere might not be toxic to them.
* The god would like to add handcrafted, inhabitable tunnels and other underground structures to the planet. Bonus points for answers that support such a design. For example, if the planet is for the most part a ball of magma, then he doesn't have much to work with.
Edit:
It seems mentioning the godlike entity has distracted from the real question, which is exactly as stated:
* Would it be possible for a solitary celestial body to sustain humanoid life?
Even supposing that it were possible, I realize that the necessary conditions would not occur naturally. By including the context of the god, I wanted to make clear that this is not a problem for me. For example, if the answer to the question requires a perfectly spherical planet made out of solid plutonium, that's what you'll get to work with. However, except for the fact that it doesn't matter where to get the materials, or how to apply or shape them, I (as in, the human being behind the computer that is writing the question) am still only interested in scenario's that make sense according to our current understanding of physics. The radiation emitted by the planet made out of plutonium should still kill every organism nearly instantly, irrespective of whether or not the godlike entity has the power to magically handwave the radiation poisoning away.
I have included the additional story-specific elements, because it might provide some insight in how useful specific answers are, or how I determine the most acceptable answer. If any of the story-specific elements are confusing, feel free to ignore them.
Also note that if the god does decide to make the laws of nature different from how we model them, than the ramifications of such alterations are best discussed in another topic. 258