Eta Carinae Nebula. Optical image of the Eta Carinae Nebula (red) and open star clusters in the constellation Carina, the keel. North is at top. This large gas cloud glows due to ionisation of the hydrogen gas it contains by radiation from hot stars embedded in it. To the left of the nebula is the dense open star cluster NGC 3532. Directly below the nebula at lower centre is the open cluster IC 2606, which contains the bright blue star Theta Carinae. The Milky Way runs through Carina, accounting for the dense starfields seen in this region. The constellation is near the southern celestial pole, and can be seen all year round for most southern hemisphere observers.