A people whose scientists proved that warp travel damages subspace, leading the Federation to impose a warp speed limit.
The Hekarans live near the Hekaras Corridor, one of the few safe passages through a region of unstable space. Their scientists, Serova and her brother Rabal, became convinced that repeated warp travel was damaging the fabric of subspace and threatening their homeworld, but the Federation dismissed their research.
To prove her point, Serova destroyed herself and her ship in a way that opened a subspace rift, which then caught the Enterprise-D. The Federation was forced to accept the danger and restricted ships to warp five except in emergencies, a rule mentioned in later stories.