system
Given the following post, respond as if you're commenting on Reddit:
human
Voyager 2 has reveled that the interstellar medium near the heliopause has a temperature of around 30,000-50,000K (29,000-49,000C). How and why doesn't Voyager just melt with such tempatures?

Is the vacuum of space the same temp or is it just the infrequent and tiny particles that are this temp? I thought space was rather cold when away from a star.
gpt
Most of the gas in space really is quite hot. Most of the volume of the "interstellar medium" - the gas distributed within a galaxy - is an ionised plasma at around 10,000 K. In intergalactic space, the gas is a hot blob of plasma that has largely been ejected from galaxies through supernova explosions, so it's at ~1,000,000 K. It's only really in dense cool molecular clouds that you get to room temperature or below.

*But* this is an extremely thin gas, and it doesn't transfer heat to solid objects very efficiently, because the rate of collisions is so low. On a human scale, it doesn't feel like a gas/plasma at all, but more like an insulating vacuum. How much a probe heats up or cools down comes down to: how much heat does it produce, how much heat is lost through radiation, and how much heat is gained from radiation. You get heated up by nearby stars and your own internal power source, and cooled down by thermal radiation.

Once you are far away from the Sun, you really don't get don't get much heat at all from the background of Milky Way stars. So the general tendency is to cool down - you emit more radiation than you receive. This is quite a slow process: for a human in a space-suit it's slowed down by your body converting food & air into heat. A human in a space-suit without heating might die of hypothermia, but it'll be over days - they won't be snap frozen like in Mission to Mars. For a probe or satellite, you can even get the opposite problem - the power source might be producing too much heat, and you need to think about how to design it to make sure it cools down.

**tl;dr** interstellar space is full of hot gas that feels cold, but not *that* cold.