Supernova 1954J (Variable 12) in NGC 2403 unmasked

We have confirmed that the precursor star of the unusual supernova 1954J ( also known as Variable 12) in NGC 2403 survived what appears to have been a superoutburst, similar to the 1843 Great Eruption of eta Carinae in the Galaxy. The apparent survivor has changed little in brightness and color over the last 8 years, and a Keck spectrum reveals characteristics broadly similar to those of eta Car. This is further suggested by our identification of the actual outburst-surviving star in high-resolution images obtained with the Advanced Camera for Surveys on the Hubble Space Telescope. We reveal this "supernova impostor" as a highly luminous (M-V(o) approximate to -8.0 mag), very massive (M-initial greater than or similar to 25 M-.) eruptive star, now surrounded by a dusty` (A(V) approximate to mag) nebula, similar to eta Car's famous Homunculus.