Star factories, celestial workshops of the cosmos, are captivating realms where the intricate dance of gas and dust gives birth to new stars. These dynamic nurseries, scattered throughout galaxies, unveil the cosmic spectacle of stellar creation.

A team of scientists, led by Chalmers University of Technology in Sweden, has delved into two early-universe galaxies boasting exceptionally productive star factories. Utilizing advanced telescopes to dissect the galaxies’ light into distinct colours, the researchers were astonished to detect light emanating from a multitude of molecules, surpassing previous observations at such vast distances. This breakthrough study holds the potential to reshape our comprehension of the dynamic lives of highly active galaxies during the early epochs of the universe.

In its youth, galaxies differed significantly from the serene spirals seen today, harbouring intense star formation concealed by dense dust layers. By scrutinizing the most remote galaxies observable with cutting-edge telescopes, astronomers gain insights into the mechanisms behind these prolific star factories.

In a recent research endeavour published in the journal Astronomy & Astrophysics, a group of scientists, spearheaded by Chalmers astronomer Chentao Yang, harnessed the observational capabilities of NOEMA (NOrthern Extended Millimetre Array) telescopes in France. Their objective was to unravel the intricacies of the star formation processes within early galaxies. Yang and team specifically analyzed the light emissions from two radiant galaxies in the early universe, including one identified as a quasar, both exhibiting elevated rates of star formation.

“We knew these galaxies were prodigious star factories, perhaps amongst the biggest the universe has ever seen. To be able to find out how they work, we measured their light at wavelengths around one millimetre, hoping to collect new clues,” says Chentao Yang.

The measurements exceeded the scientists’ expectations, revealing a wealth of information. The light captured from both galaxies unveiled traces of diverse molecules emitted from the depths of these stellar nurseries, where clouds of gas and dust give rise to new stars in various wavelengths.

Through a meticulous analysis of each galaxy’s spectrum—the unique colours within their light—the scientists successfully identified 13 molecules. Notably, some of these molecules had never been observed before in galaxies at such great distances. Each molecule serves as a valuable indicator, offering insights into the temperature, pressure, and density within interstellar spaces. Moreover, they shed light on the intricate interactions among starlight, radiation, and matter, furnishing crucial new details about the physical and chemical conditions prevailing in these distant galaxies.

The light from the two galaxies investigated by the research team travels such vast distances that it takes nearly 13 billion years to reach us.

“Looking at these galaxies is less like a night under the stars and more like seeing a city lit with neon lights,” says Susanne Aalto, Chalmers astronomer and team member.

Astronomers routinely capture images of star-forming regions within our galaxy, such as the Orion Nebula and the Carina Nebula, as part of their observational practices, she elaborates.

“In these two distant galaxies, we are instead seeing star factories that are bigger, brighter, full of dust, and different in many ways. The Orion and Carina nebulae are lit up thanks to ultraviolet light from hot, newborn stars. In these two distant galaxies, ultraviolet light can’t get past the layers of dust. Much of the illumination is instead thanks to cosmic rays — high energy particles that can be created by exploding stars, or close to a supermassive black hole,” says Susanne Aalto.

Although galaxies resembling these two are uncommon, the researchers have intentions to investigate more instances of star factories utilizing both NOEMA and its larger counterpart, ALMA (the Atacama Large Millimetre/Submillimetre Array) located in Chile. Both telescopes possess sensitivity to light with wavelengths around one millimeter.