astrochemical

Astrochemical is a term used to describe the chemical processes and species studied in space, collectively forming the field of astrochemistry. The science sits at the intersection of astronomy, chemistry, and physics and aims to explain how molecules form, persist, and evolve from the diffuse interstellar medium to planetary systems.

Key environments include the diffuse and dense interstellar medium, dark molecular clouds, star-forming regions, hot cores, protoplanetary disks, cometary comae, and the atmospheres of planets and evolved stars. Molecules arise through gas-phase reactions, grain-surface chemistry on dust grains, and processing of icy mantles by ultraviolet photons and cosmic rays. Destruction occurs via photodissociation, shocks, and freeze-out, while excitation gives rise to observable spectral lines.

Observations rely on spectroscopy across radio, millimeter, submillimeter, and infrared wavelengths. Notable milestones include the detection of molecular hydrogen, carbon monoxide, water, ammonia, methanol, and a growing suite of complex organic molecules. Facilities such as ALMA, Herschel, Spitzer, and various radio telescopes enable comprehensive surveys and high-resolution imaging. Laboratory astrochemistry and theoretical chemistry provide reaction rates and spectra under space-like conditions, and computational models reproduce the chemistry at the low temperatures and pressures typical of astronomical environments.

Modeling and databases underpin the field. Chemical networks, using databases such as UMIST and KIDA, simulate kinetic evolution and are coupled with physical models of clouds, disks, or envelopes. Astrochemical research informs the chemical evolution of galaxies, the formation of stars and planets, and the potential delivery of water and prebiotic molecules to nascent worlds, while facing challenges such as uncertain low-temperature rates and the complexity of grain-surface chemistry.