What characterizes the hydrogen state in molecular nebulae environments?

Hydrogen exists primarily as molecules (H2) rather than individual atoms.

Molecular nebulae represent the most extreme physical conditions within the interstellar medium regarding temperature and density, specifically ranging around 10 to 20 Kelvin. These cold, dense conditions are crucial because they allow hydrogen atoms to pair up and bond, forming molecular hydrogen ($ ext{H}_2$). In contrast, warmer regions of space feature atomic hydrogen. The formation of stable molecules signifies the low energy state and high concentration required for gravity to begin dominating internal pressures, marking these areas as the primary sites where stellar collapse can successfully initiate.