Any alien race with technology to reach Sol will also have superior technology to defend themselves. Only start worrying when the “balloon” shot down the F-18s and F35s that were scrambled to shoot it down.
Actually I was surprised to find this isn't _strictly_ true, but it is likely.
One possibility is other solar systems (far away) with a different blend of materials that make certain advancements "easier". One hypothetical example is a far away solar system having high quantities of "exotic" stable super-heavy elements that make things like FTL possible.
In such a scenario we wouldn't discover it because it's not naturally occurring in our solar system, and we wouldn't stumble on it until we built a large enough particle accelerator. So another race could be _way_ ahead of us with respect to FTL, but way behind us in things like material science or computers. Imagine if their solar system was completely missing say... silicon.
It's called the solar system. "Sol" is not an official name.
Also el sol (es), o sol (pr), il sole (it), le soleil (fr), etc.
Technically the IAU hasn't sanctioned an official name, but Sol is fairly well understood.
[0] https://earthsky.org/space/what-is-the-suns-name/
[1] https://www.iau.org/public/themes/naming/
[2] List of IAU Solar System Objects, Exoplanets, Starts, and Stellar Streams https://docs.google.com/spreadsheets/d/1CEXGyancLRtHyPW7u0L_...