Eta Carinae nebula. Artwork of the nebula surrounding the star Eta Carinae. The nebula has two spherical lobes with a thin equatorial disc between them. Eta Carinae is a wildly unpredictable star. In 1843 it was the second brightest star in the sky, but it is currently barely visible with the naked eye. It is thought that this is due to an explosion casting off a huge sphere of material. As this cooled it became opaque, gradually cutting out the star's light. Eta Carinae is around 6000 light years from Earth in the constellation Carina.