The aromatic UNIVERSE

Over the past 20 years, ground- and space-based observations have revealed that the universe is filled with molecules. Astronomers have identified nearly 200 types of molecules in the interstellar medium (ISM) of our galaxy and in the atmospheres of planets; for the full list, see www. astrochymist. org. Molecules are abundant and pervasive, and they control the temperature of interstellar gas (see the box on page 40). Not surprisingly, they directly influence such key macroscopic processes as star formation and the evolution of galaxies.