Outer space
Interstellar space is the physical space in a galaxy not occupied by stars or their planetary systems. It continues to the edges of the galaxy, where it fades into the intergalactic void. Most of the mass in this space is made up of single hydrogen atoms, fewer helium atoms and a few heavier atoms formed in stars. Supernovae blow some of their atoms huge distances. A number of molecules and tiny 0.1 μm dust particles do exist in interstellar space. About four new types of molecule are discovered each year. Large regions of higher density matter known as molecular clouds allow chemical reactions to occur. This includes organic polyatomic species. Much of this chemistry is driven by collisions.