Interstellar space is not as empty as you might think. There’s gas stretching from star to star, and also microscopic grains of cosmic dust. While dust on Earth is mostly a pain to clean, cosmic dust is fundamental in creating the seeds that eventually forms planets.

Astronomers have been trying to work out the many processes that produce dust in the universe, and a team lead by researchers from the University of California, Los Angeles have discovered that large collections of stars are actually forming and expelling cosmic dust, something that was only theorized before.

“People have looked for this large-scale enrichment of galaxies, but they haven’t seen it before,” team leader Professor Jean Turner said in a statement. “We’re seeing galaxy-scale enrichment and we see clearly where it is coming from.”

The team used the Atacama Large Millimeter/submillimeter Array (ALMA) to study galaxy II Zw 40, which is roughly 33 million light-years away.  ALMA can see what the human eye cannot, and it’s used to study cold components in the universe, like gas and dust. The researchers picked II Zw 40 because it has one of the largest star-forming regions in the known universe.

“We’re looking at the best place to see dust enrichment, in large star clusters,” lead author S. Michelle Consiglio stated.

The observations, published in the Astrophysical Journal Letters, focus on the central region of the galaxy where one could find two young stellar clusters, each with about 1 million stars. The team mapped where the dust is and it is concentrated within 320 light-years from the clusters.

“The double cluster is a ‘soot factory’ polluting its local environment,” Consiglio said.

“The evolutionary time scales of these stars are short enough that you see the dust before it has a chance to get dispersed very far from its source,” added Turner.

While the result is important in understanding the dust cycle in galaxies, the observations are a single snapshot of the process. Researchers plan to look at many more stellar clusters of different ages so they can produce a full picture of how galaxy dust enrichment happens.