Astronomers seeking to understand the process of star formation have brought together images from three of the world's great telescopes. The images they made will be the basis of future research into why stars form in some locations and not others and have created a feast for the eyes of the rest of us.

That stars condense out of huge balls of gas is well known, as is that disturbances from nearby objects can initiate the process. Nevertheless, the details of something apparently so simple remain surprisingly obscure. We can observe stellar nurseries in our own galaxy and others in the local group but we only see snapshots of a process that takes millions of years.

The European Southern Observatory has combined the power of its Very Large Telescope (VLT) and the Atacama Large Millimeter/submillimeter Array (ALMA) with the Hubble Space Telescope's vantage point to examine 90 galaxies at a variety of wavelengths with previously impossible resolution.

"For the first time we are resolving individual units of star formation over a wide range of locations and environments in a sample that well represents the different types of galaxies," said the ESO's Professor Eric Emsellem in a statement, "We can directly observe the gas that gives birth to stars, we see the young stars themselves, and we witness their evolution through various phases."

Emsellem and colleagues from 30 institutions filtered VLT images to highlight the warm gas surrounding newborn stars, showing where in the galaxies star formation is occurring. These were then merged with ALMA images of the same galaxies at frequencies where cold gas clouds are bright.

Between the two we can see where stars are emerging contrasted with the places where there is plenty of raw material to make stars, but the process has not begun. "Are stars more often born in specific regions of their host galaxies – and, if so, why? And after stars are born how does their evolution influence the formation of new generations of stars?” asked the University of Heidelberg's Dr Kathryn Kreckel. 

Together, team member Dr Francesco Belfiore of Italy's INAF-Arcetri said; they were able to take; “Images sharp enough to see the individual clouds, stars, and nebulae that signify forming stars” for the first time.

To help our brains comprehend what we are seeing, radiation at wavelengths far beyond the capacity of the human eye is shifted to certain colors, while the images taken in visible light are represented by others.

“This will give us a chance to better understand what triggers, boosts or holds back the birth of new stars,” Dr Rebecca McElroy of the University of Sydney said.