Astrochemie

Astrochemistry, often spelled astrochemie in non-English contexts, is the branch of science that studies the chemical processes that occur in astronomical environments. It seeks to understand how atoms form molecules in space, how those molecules are formed and destroyed, and how chemical networks evolve across different celestial environments, from interstellar clouds to planetary systems and comets.

The main settings include cold, sparse interstellar and circumstellar gas, dense molecular clouds where stars and planets form, and the icy mantles on dust grains. In these environments, gas-phase reactions, grain-surface chemistry, and energetic processing by UV photons and cosmic rays drive the synthesis of simple and complex molecules, including organic species.

Observational astrochemistry relies on spectroscopy across radio, millimeter, infrared, and occasionally ultraviolet wavelengths to identify molecular fingerprints. Telescopes such as ALMA and space facilities detect rotational and vibrational transitions of molecules. Laboratory experiments simulate interstellar ices and reaction conditions, while theoretical models calculate reaction networks and steady-state abundances.

Historically, the field emerged in the mid-20th century with the first detections of simple diatomic and radical species in the interstellar medium. Developments in spectroscopy and laboratory astrophysics enabled discoveries of increasingly complex organics, including prebiotic molecules, revealing a possible chemical pathway for the origin of life and guiding studies of planetary formation.

Subfields include gas-phase chemistry, surface chemistry on dust grains, ice chemistry, isotope effects, and astrochemical modeling. Astrochemistry informs the chemistry of protoplanetary disks, comets, and exoplanet atmospheres, and intersects with astrobiology by exploring how complex organic molecules form and survive in space despite harsh conditions.