system
Given the following post, respond as if you're commenting on Reddit:
human
Why is the Local Interstellar Cloud (still) so hot?

According to Wikipedia "[...] The cloud has a temperature of about 6,000 K,[2] about the same temperature as the surface of the Sun. However, its specific heat capacity is very low as it is not very dense, with 0.3 atoms per cubic centimeter [...]

1. How come it's so hot? 
2. How does it stay that hot considering the small density and the matter being surrounded by cold vacuum?
3. Is our solar system "swimming like an ice cube" through the cloud?
gpt
1.  Don't confuse heat with energy.  Heat is simply the speed at which molecules are moving - the gas molecules are zipping around in the cloud at a pretty good clip, thus it is hot - but the actual energy density is very small. 

2.  It's not despite the vacuum, but rather because of it.  There is no convective cooling in a vacuum, leaving emissive cooling as the only method in play.  There's simply nowhere for the energy to go. 

3.  Swimming like an ice cube...I haven't heard that one before.  Our solar system is a mostly empty vacuum and what does not exist is not interacting with the cloud.  Large masses (planets, stars, etc) will collect the matter that becomes trapped in their gravity wells a bit like a cosmic vacuum cleaner (there's a pun in there somewhere) but other than that, the intersections of the cloud's matter and the solar system's matter are relatively minimal.