The destination
Proxima Centauri is the nearest star to the Sun, a red dwarf of spectral type M5.5V about 4.24 light-years (1.30 parsecs) away. It has about an eighth of the Sun’s mass and a surface temperature near 2,900 K. Its planet Proxima b was found in 2016 by measuring the star’s wobble, and it orbits at 0.0486 AU, much closer than Mercury is to the Sun, completing an orbit every 11.19 days.
Because the star is so dim, that close orbit puts Proxima b inside the habitable zone: it receives about 65 % of the energy Earth gets from the Sun. The wobble method gives only a minimum mass, 1.07 ± 0.06 Earth masses (ESPRESSO data, 2022). The true mass depends on the orbit’s tilt, which is not known. The planet does not pass in front of its star, so its radius is unknown too. No image of it exists. Every picture of Proxima b, including the one on this page, is an artist’s impression.
The hard problems
Distance. At 4.24 light-years, it is about 270,000 times farther away than the Sun. The fastest spacecraft launched so far would take thousands of years. The Breakthrough Starshot study proposes gram-scale probes on light sails pushed by ground-based lasers to roughly 15–20 % of light speed; at 0.2 c the trip takes about 21 years, before any time to accelerate.
Communication. A signal takes 4.24 years each way. Any question asked from Earth gets its answer more than eight years later. Anything that happens at Proxima b has to be handled there.
The star. Red dwarfs flare. Proxima Centauri produces frequent flares, and in 2016 one was bright enough to have been visible to the naked eye. A planet this close receives the radiation and particles from those events at full strength, and whether it keeps an atmosphere at all is an open question.
Light and rotation. The planet is probably tidally locked, keeping one face to the star, or caught in a resonance such as three rotations per two orbits. A locked planet has a permanent day side and a permanent night side, and its climate depends on whether an atmosphere carries heat between them.
What this campaign models
Campaign 05 is a concept study, not a settlement plan. It models the crossing: launch energy, sail and laser constraints, the length of the trip, and what a probe could report back. Where we have to choose a value that nobody knows, such as the planet’s radius or atmosphere, the campaign shows the choice and its range.
Status
Concept. Campaign 05 is a long-range study and the last stop on the Galaxy Campaign route.