# A planetary system around the nearby M dwarf GJ 667C with at least one super-Earth in its habitable zone

A planetary system around the nearby M dwarf GJ 667C with at least one super-Earth in its habitable zone.

Just 6.97 parsecs away, which is 22.7 light years – a century via a fusion rocket or laser-sail or an episode on “Star Trek”. Given large solar collectors at 0.1 AU from the Sun and the mass-beam projectors parked at both ends, then a manned starship might do the trip in ~26.4 years at 0.9c. At 1 gee it takes exactly 2 years Earth-time to accelerate to 0.9c, while travelling ~2.5 light-years to get up to speed, then brake, thus cruising ~20.2 light-years. Total trip-time for the travellers is 12.6 years. The trick for mass-beam starships will be getting up to speed in a reasonable aiming distance for the mass-beam projectors. Pushing hard at 25 gee would allow cruise speed to be reached in just 0.05 light-years, but will require the crew enduring 21 days of high-gees at each of the journey. In theory they could float in oxygenated fluid, but in practice that’s largely an under-developed technology which only features in SF – like “The Forever War” (Joe Haldeman) and “Fiasko” (Stanislaw Lem).

One-gee allows 0.5c to be reached in just 0.15 light-years, which might be more feasible if the high-gee option deters would be relativistic travellers. Of course if we had a 1 gee space-drive, just how long does the journey take? On board the ship it’s 6.27 years, while in the Galaxy’s reference frame it’s 24.6 years of travelling. However from the PoV of an observer on Earth a return signal indicating arrival at GJ667C takes ~47.3 years, while a signal indicating the ship’s departure only arrives 1.9 years before the 1-gee starship does, for the observer at GJ667C. Relativity messes with our perceptions in more ways than one.