So does that mean that past the termination shock and heliopause, there is nothing but plasma-temperature material? If so, can we get passed it in a ship? Or would it be impossible because of the temp?
Good question. The simple answer is we are not even concerned with problems to space travel in that region as we will not get to do it for many hundreds of years. The physicists are just trying to explain how the sun and solar system interact within the galaxy. Can you build a spacecraft with enough oxygen, food, water to last at least 30 years, 50 years? Nearest planets outside our solar system is about 11 light years away, 1 light year is how much distance light travels in a year. 1 light year is 6 trillion miles, so to go 60 trillion miles at a modest speed of 20,000 miles per second it will still take you 30 million seconds which is about a year. 20,000 miles per second is 72,000,000 miles per hour. We cannot make things go faster than 10 Mach with efficiency, space shuttle does 7 Mach, i doubt we will ever get something as big as a space ship to travel fast enough for humans to leave the solar system alive. Takes us 6 months to get to Mars, and its closest point is 36 million miles.
Temperature in itself is not the big problem i think, maybe a solution as we would freeze to death in the empty space. Temperature and heat are sometimes interchanged. Temperature is a measure of disorder, to put it simply. Like in a gas it is determined by the speed, therefore energy, of the gas molecules and how they bounce off the walls. It is all the radiation that would transfer energy, and heat is energy while temperature is not energy, but it can be related to it via certain phenomena and equations. There is not enough gas density i think for temperature to be an issue.
The question is can you shield a spacecraft to withstand all that radiation. Remember, radiation does not require a medium to travel through, it travels at the speed of light in vacuum. If it has no humans it can be easy, but for living things inside it gets tricky. High energy radiation penetrates materials.
To talk about plasma i would have to think about it. It is complicated, as this passage shows. The Nature article is even more trickier with terms that not many would know.
Prior to the actual event, researchers had expected a fairly simple crossing, with the probe moving from a region where the solar wind was supersonic to one where it was subsonic. What they found instead was a "complex, rippled, quasi-perpendicular supercritical magnetohydrodynamic shock of moderate strength undergoing reformation on a scale of a few hours." Instead of moving through the shock front once, Voyager 2 underwent five distinct crossings over a two day period. This was due to the dynamic nature of termination shock fluctuations; in fact, the time between crossings is on the order of magnitude expected for ripples propagating through the shock.
