Starburst galaxies create more stars at a faster pace, up to 1,000 times faster, than spiral galaxies like our Milky Way. Researchers using the Atacama Large Millimeter/submillimeter Array (ALMA), set out to discover why this is and what they found has long term implications for the growth and evolution of galaxies.

“All stars form in dense clouds of dust and gas. Until now, however, scientists struggled to see exactly what was going on inside starburst galaxies that distinguished them from other star-forming regions,” said Adam Leroy, an astronomer formerly with the National Radio Astronomy Observatory (NRAO) in Charlottesville, Virginia in a statement.

ALMA, built as a collaboration between Europe, North America and East Asia in cooperation with the Republic of Chile changes the equation by allowing astronomers to resolve individual star-forming structures, even at a great distance.

The team used ALMA to examine star forming clouds in NGC253, a starburst galaxy 11.5 million light years from the milky way. Specifically, they mapped the distribution and motion of multiple molecules within star forming clouds at the core of NGC 253, commonly known as the Sculptor Galaxy.

The Sculptor Galaxy, also sometimes known as the as the Silver Coin or Silver Dollar Galaxy, is in the constellation Sculptor. It was discovered by Caroline Herschel in 1783 during a comet search. NGC 253 is part of the Sculptor Group, one of the closest clusters of galaxies to the Milky Way.

Although supernovae tend to be common in starburst galaxies, only one SN 1940E, has been found in the Sculptor Galaxy. A slumbering supermassive black hole, 5 million times the mass of our sun, lies at the center of it ready to add to the chaos.

With earlier telescopes, it was difficult to identify and research specific stellar nurseries because they tended to blend together. However, ALMA’s resolution and sensitivity allowed the researchers to identify ten distinct stellar nurseries in the heart of Sculptor.

“There is a class of galaxies and parts of galaxies, we call them starbursts, where we know that gas is just plain better at forming stars. To understand why, we took one of the nearest such regions and pulled it apart – layer by layer – to see what makes the gas in these places so much more efficient at star formation,” said Leroy

The team mapped the distribution of 40 millimeter-wavelength “signatures” emitted by different molecules inside the center of Sculptor. The presence and activity of different molecules tell astronomers a great deal about what is going on because they correspond to different activities and conditions within star-forming clouds.

Carbon monoxide (CO), for example, appears in massive envelopes of lighter gas that surround seller nurseries. Hydrogen cyanide (HCN), on the other hand, appears in dense areas of active star formation. Molecules like, like H13CN and H13CO+, appear in denser regions still.

By mapping the distribution, motion and concentration of these molecules, the researchers were able to dissect the star-forming clouds and show that they were ten times denser than similar clouds in spiral galaxies.

The differences suggest that it’s the type of stellar nurseries and not just the number of them that account for the accelerated pace of star formation. Because the stellar nurseries of starburst galaxies have so much dense material available, stars are formed much more quickly.

“These differences have wide-ranging implications for how galaxies grow and evolve. What we would ultimately like to know is whether a starburst like Sculptor produces not just more stars, but different types of stars than a galaxy like the Milky Way. ALMA is bringing us much closer to that goal,” said Leroy.

These latest results were presented at a February 15 news conference at the American Association for the Advancement of Science (AAAS) meeting in San Jose, California and have been accepted for publication in the Astrophysical Journal.