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Stars, planets, comets, and nebulas are made of the same atoms we see on Earth: the same periodic table seems to govern all ordinary matter, everywhere. Astrochemistry is the way for researchers to study how those atoms react with each other across wildly different environments, producing both familiar and exotic molecules. Those molecules constitute the dust that makes planets, and organic compounds that are the precursors to life.

From Very Small to Very Large and Back Again

Quantum physics tells us that every atom and molecule has a distinct spectrum of light emission and absorption, based on interactions between the electrons and nuclei. By studying the colors of light produced and absorbed by stars, nebulas, and other astronomical objects, astronomers have learned they are made up of the same stuff as matter on Earth.

Environments across the universe can be radically different than Earth, though. Chemistry takes place at very hot or cold temperatures, under huge pressures or low densities, in the presence of intense radiation from stars or inside dark nebulas. As a result, astrochemists study the way chemical bonds form under interstellar conditions which are very alien to us, using astronomical observations, theoretical calculations, and laboratory experiments.

One particular area of interest is the formation of organic molecules, which are compounds including the element carbon. Beyond its essential role in all known life, carbon is one of the most common elements in the universe, and it forms molecules with many other elements. In interstellar space, carbon is the main ingredient of dust: aggregates of molecules that form wispy clouds. Dust is an important component of new stars and planets; knowing how it forms and behaves is necessary for understanding our own origins, as well as other planets.

Astrochemistry also plays a role in studies of the atmospheres of stars and planets. Current and upcoming observatories are designed to detect the chemical elements making up planetary atmospheres, looking for molecules like water and carbon compounds.

 

Artistic depiction of polycyclic aromatic hydrocarbons (PAHs), complex organic molecules discovered in an interstellar cloud. These molecules provide a connection between astrochemistry and similar molecules common on Earth.

B. McGuire, B. Saxton (NRAO/AUI/NSF)