HD 20782 b is the standard answer for the exoplanet with the most eccentric confirmed orbit, with an eccentricity of about 0.97. Its orbit is stretched almost into a straight line rather than resembling the near-circular paths of most planets.
The planet orbits HD 20782, a Sun-like star approximately 117 light-years away in the constellation Fornax. It travels around a semi-major axis of roughly 1.36 astronomical units and takes about 586 days to complete an orbit. The system was discovered through the radial-velocity method, which measures the star's motion caused by the planet's gravity.
Because of its extreme eccentricity, HD 20782 b experiences enormous changes in stellar irradiation. Near apastron it is relatively distant and cold; near periastron it sweeps close to its star and receives a powerful burst of energy. That makes it an important laboratory for studying atmospheric survival under dramatic climate swings.
HD 80606 b is a frequent mix-up because it also has an unusually eccentric orbit and dramatic seasons. However, HD 20782 b is the canonical answer for the approximately 0.97 eccentricity record commonly cited in exoplanet references.