Proxima b is very promising. It orbits a red dwarf star called Proxima Centauri in a system with three stars in it. Proxima Centauri is small. It only has between 7.5% and 50% of our Sun’s mass.

News that a NASA scientist has announced fresh progress on Proxima b has pushed our nearest known exoplanet neighbor back into the spotlight, sharpening long-running questions about whether this rocky ...