Well, well...
You can drag about it for a while but, let's settle this.
With facts out of a physics lexicon/textbook and whatever I managed to learn during six years.
What's heat?
The definition says that heat is the average kinetic energy the particles have that make up the object. It goes for gases as well.
In space there is virtually nothing!!!
*actually that's a lie, there are all kind of praticles goin around thanks to the stars, but photons aren't to be treated as acouple of heavy protons, they "weigh" a lot less (please don't get into this I know that you can't really say that a photon has mass).*
So tell me how hot is it in space???...
After all the very question is "dumb" if you think about it.
Space can't have any heat, or temperature, because there's nothing to carry that kinetic energy.
That's why we say that only space is close to absolute zero *minus 273 celsius or 0 kelvin*, becasue if you were to ever measure that temperature everything would be without kinetic energy, ergo there would be no heat.
So in space an object can have its heat of its own, but not the environment.
Radiation - all forms of radiation, such as light , gamma rays, alpha particles *He2+*, neutron stream whatever else - generates heat when it hits an atom. For that instance the atom of a ship's hull or it's radiator.
The ammount depends on the radiation which depends on the distance form the source. So if you're in Earth orbit you're in trouble, 'cause the radiation is enough to keep the planet's ecosphere going even with the atmosphere's dampening.
However each material has its own reflection factor. That's why NASA paints all their equipment white - so they reflect as much radiation as possible.
Moreover objects normally radiate. A black object *physics term an object that only emits radiation but does not reflect any.* radiates on all frequencies, but with a different amplitude. The amplitiude-frequency curve's shape, the amplitudes and position of its maximum depend on the temperature, and the temperature alone.
So hot objects radiate more and on higher freuencies. Every object around you radiates - but not necessarily on visible wavelenghts.
The trick in space is to give off more heat than what you accumulate. So you need big heatsinks in the in the dark side of the ship *the one not facing a star*.
