How Do Molecules Form in Space?
The destruction of the first Population III stars in spectacular supernovas sprinkles interstellar space with clouds of heavy chemical elements. These clouds are drawn together by gravity, producing a second generation of smaller, longer-lived Population II stars. Many stars visible in the night sky are of this type.
The clouds are cold and dark, but when the density of hydrogen atoms is high enough, hydrogen molecules form. Carbon and oxygen atoms combine to form carbon monoxide and carbon dioxide. Molecular nitrogen and oxygen may also form. Hydrogen and oxygen combine to form water molecules.
Towards the ends of their lives, some Population II stars may swell in size to become red giants, producing tiny graphite and silicate particles in a smoky haze around their outer layers. These particles provide catalytic surfaces on which atoms can combine to produce more complex molecules. We now know of about 140, possibly including glycine, the simplest amino acid.
So, when the clouds created by the death of Population II stars gather together once more they are already relatively rich in complex molecules. Such giant molecular clouds condense to form third-generation Population I stars complete with their own planetary systems.
The Sun’s nursery may have contained important life molecules.