Milky Way. Optical image of the Milky Way galaxy, centred on the dark Coal Sack Nebula. North is at top. The Coal Sack is a cloud of dust and gas that blocks the light from the dense starfields behind it. Just above and to the right of the Coal Sack are the four stars of the Southern Cross constellation (Crux Australis). The two bright stars at centre left are part of the constellation Centaurus. They are Alpha (far left) and Beta Centauri. The pink area at far right is the Eta Carinae Nebula, a giant emission nebula in the constellation Carina. This large gas cloud glows due to ionisation of the hydrogen it contains by radiation from hot stars embedded within it.