Hubble Space Telescope Proper-Motion Measurements of the η Carinae Nebula

Abstract

We present proper-motion measurements of the bipolar lobes and equatorial disk features ejected from η Carinae during the last century and deduce their relative ages in order to determine the likelihood of multiple ejection events. Hubble Space Telescope Wide Field Planetary Camera 2 images taken in 1994, 1995, and 1999 were compared, and the motions of small (~1") patches throughout the nebula were measured. Assuming that the material has not been accelerated or decelerated, the projected expansion velocities of both lobes and two equatorial features (the ``Paddle'' and regions in the NN Jet) indicate that the bipolar lobes and fast equatorial ejecta have the same origin date, some 150 years ago during the Great Eruption. We also conclude that the ejection of the partial shell of outer debris preceded the Great Eruption by at least several decades or possibly a century, confirming that the nebula surrounding η Car represents at least two outburst events and maybe more. Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., for NASA under contract NAS5-26555.