The systemic velocity of Eta Carinae*

High-resolution spectra of molecular hydrogen in the Homunculus nebula allow for the first direct measurement of the systemic velocity of η Carinae. Near-infrared long-slit data for H₂ 1-0 S(1) λ21218 obtained with the Phoenix spectrometer on the Gemini South telescope give V_sys=-8.1 +/- 1 km s^-1 (heliocentric), or V_LSR=-19.7 +/- 1 km s^-1, from the average of the near and far sides of the Homunculus. This measurement considerably improves the precision for the value of -7 +/- 10 km s^-1 inferred from neighbouring O-type stars in the Carina nebula. New near-infrared spectra also provide a high-resolution line profile of [FeII]λ16435 emission from gas condensations known as the Weigelt objects without contamination from the central star, revealing a line shape with complex kinematic structure. Previously, uncertainty in the kinematics of the Weigelt knots was dominated by the adopted systemic velocity of η Car.