Eta Carinae Left a Curious Ladder to Climb

Eta Carinae underwent the Great Eruption in the 1840s and a Lesser Eruptionin the 1890s. Its apparent spectrum, modified by intervening ejecta, theHomunculus and Little Homunculus, continues to evolve but contains informationpertaining to events in the 19th century. The LOS spectrum contains narrowabsorption velocities, from -122 to -1665 km/s: rungs of a broken ladder causedby shells formed by the interacting winds. Estimated shell origin datescorrelate with origin dates of expanding emission structures preceding theGreat Eruption. The LOS absorption velocities extend the record post GreatEruption to the Lesser Eruption. We suggest that these shells originated from abinary merger within a triple system. Shells formed not only from periastronpassages of the current secondary, but also from ear-like extensions precedingand following the periastron event. Additional models need to be considered.