Eta Carinae and Homunculus nebula, illustration. Eta Carinae is a binary star system that lies around 7,500 light years from Earth in the constellation Carina. In the mid 19th century it underwent an eruption that made it the second brightest star in the night sky for a period. The gaseous shell ejected during this eruption has formed a twin-lobed dust-filled nebula around the stars known as the Homunculus nebula.