Eta Carinae Nebula (NGC 3372), optical image. This nebula (a vast cloud of dust and gas) surrounds the variable star Eta Carinae. This massive star, over 100 times the mass of the Sun, is the most luminous star known in our galaxy. It radiates its energy at a rate that is 5 million times that of the Sun. Because of its huge mass, it is extremely unstable. It is in the constellation Carina, about 9000 light years away from Earth. This image includes filters for the light from hydrogen (H-alpha), oxygen (OIII) and sulphur (SII) ions.