Animation of a flight into a dense cloud of dust within a bright emission nebula. Emission nebulae glow pink due to ionisation of the hydrogen gas they contain by the radiation from hot young stars recently born within them. The densest regions of gas and dust block starlight and appear dark against the glow. The most dense regions are known as Bok globules, and contain a few Suns' worth of mass in a region around a light year across, and are in the process of collapsing into new stars.