Radio telescopes help scientists map molecules in space and uncover where and how stars form

Radio telescopes have revolutionized the way scientists map molecules in interstellar space and uncover the origins of star formation. Carl Sagan's quote "we are made of star-stuff" highlights the fact that elements heavier than hydrogen and helium are created in the centers of the first stars. Astrochemists and radio astronomers like myself study the chemistry of interstellar laboratories, focusing on how simple ingredients combine to form larger molecules, including those essential for life.

To map molecules in space, researchers analyze the distribution of molecules in terms of abundance, temperature, and motion. Technological advancements have enabled more precise mapping of these metrics. My research team recently compared newer methods with previous maps to ensure the consistency of earlier findings.

Molecular clouds, the cosmic nurseries where stars form, are initially extremely cold at around -442°F (-263°C) and have a low density of about 100 molecules per cubic centimeter. As stars form, temperatures rise to between -279°F and -100°F (-173°C to -73°C), and density increases to 10 million molecules per cubic centimeter or more. These conditions facilitate the fundamental chemical reactions that occur in interstellar laboratories.

However, these laboratories are too distant for direct observation. My focus is on high-mass, star-forming regions, such as the Orion Kleinmann-Low nebula (Orion KL), located about 1,300 light-years away from Earth. Unfortunately, I cannot physically visit Orion KL or witness the formation of stars and molecules in real-time. Instead, I observe the chemistry of Orion KL from Earth using radio telescopes.

Radio telescopes detect radio waves emitted by molecules, allowing astronomers to analyze the signatures of interstellar chemistry. Radio waves have longer wavelengths than visible light, which telescopes equipped to capture radio light can observe. Each molecule has unique radio frequencies, serving as a molecular fingerprint. By comparing the relative sizes of different signals in a spectrum, scientists can calculate quantities like molecule abundance and temperature.

Larger radio telescopes provide higher spatial resolution, enabling the observation of smaller-scale phenomena. Single-dish telescopes, up to 1,640 feet (500 meters) across, can see structures down to about 2,600 astronomical units (au) across. However, to study chemical patterns on solar system scales of about 200 au, scientists require even larger telescopes.

The radio interferometer I use, the Atacama Large Millimeter/submillimeter Array (ALMA), located in northern Chile, consists of 66 antennas that can be combined to create a telescope as wide as 10 miles (16 kilometers) across. At the frequencies where I can observe target molecules, ALMA needs to be in a configuration capable of zooming into structures only a few au across in Orion KL.