thumb|right|Animation showing the expanding light echo caused by the η Carinae eruption in the Carina Nebula Direct spectral observations did not begin until after the Great Eruption, but light echoes from the eruption reflected from other parts of the Carina Nebula were detected using the U.S. National Optical Astronomy Observatory's Blanco 4-meter telescope at the Cerro Tololo Inter-American Observatory. Analysis of the reflected spectra indicated the light was emitted when η Carinae had the appearance of a G2-to-G5 supergiant, some 2,000 K cooler than expected from other supernova impostor events. Further light echo observations show that following the peak brightness of the Great Eruption the spectrum developed prominent P Cygni profiles and CN molecular bands, although this is likely from the material being ejected which may have been colliding with circumstellar material in a similar way to a type IIn supernova.
thumb|right|Animation showing the expanding light echo caused by the η Carinae eruption in the Carina Nebula Direct spectral observations did not begin until after the Great Eruption, but light echoes from the eruption reflected from other parts of the Carina Nebula were detected using the U.S. National Optical Astronomy Observatory's Blanco 4-meter telescope at the Cerro Tololo Inter-American Observatory. Analysis of the reflected spectra indicated the light was emitted when η Carinae had the appearance of a G2-to-G5 supergiant, some 2,000 K cooler than expected from other supernova impostor events. Further light echo observations show that following the peak brightness of the Great Eruption the spectrum developed prominent P Cygni profiles and CN molecular bands, although this is likely from the material being ejected which may have been colliding with circumstellar material in a similar way to a type IIn supernova.