[The Sons of Liberty]

The planet orbits within a "temperate" zone from its host star Proxima Centauri, some four light years from us

They make it sound like it's right next door (OK, it is in galactic terms) but since we've gotten no where close to the speed of light, those "Four Light Years" would take us about 70,000 years to cross, but who knows, maybe the aliens have faster ships.

[LibWhacker]

No... Read about Starchip, which could be the next step in getting robotic probes there and learning a lot more about the Alpha-Centauri system. We could start getting Starchip probes on-site in about 40 years, the same length of time the Voyager spacecraft have been flying.

Meantime research into other forms of propulsion isn't lacking in good ideas for sending humans deep into interstellar space. Not going to happen in my lifetime, but I'm optimistic long term.