The Great Nebula in Carina . ... Eta Carinae , the most energetic star in the nebula, was one of the brightest stars in the sky in the 1830s, but then faded dramatically. Eta Carinae is the brightest star near the image center, just left of the Keyhole Nebula . While Eta Carinae itself maybe on the verge of a supernova explosion, X-ray images indicate that much of the Great Carina Nebula has been a veritable supernova factory . ... NASA Web Site Statements, Warnings, and Disclaimers . ...