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Astronomers show how ‘spiral arms’ feed young, developing stars

An international team of astronomers have discovered the exact process of how high-mass stars are born.

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An international team of researchers including astronomers from the University of Tasmania have discovered the exact process of how high-mass stars are born.

High-mass stars are like the atomic factories of the universe, generating many of the building blocks necessary for life; when they are young they are known as ‘protostars’.

Using powerful radio telescopes from across the University of Tasmania’s telescope network in Mount Pleasant (TAS), Ceduna (SA) and Katherine (NT), as well as others from across the world, astronomers have shown in recent years that high-mass stars more than eight times the size of the Sun form at the hearts of enormous rotating disks of gas and dust.

These researchers have discovered channels of gas within the spinning disk which were illuminated by a heat-wave created by material dropping from the disk onto the high-mass protostar in intense, short bursts.

By studying the characteristics of one particular high-mass protostar, known as G358-MM1, they have now, for the first time, shown exactly how these disks feed the young, high-mass star: through spiral arms.

University of Tasmania Professor in Physics and Dean of the School of Natural Sciences Simon Ellingsen worked with researchers Gabor Orosz and Lucas Hyland on the project, and said G358-MM1 has four spiral arms that wrap around it.

“The spiral arms help to feed disk material down to the inner part of the system, where it can reach the protostar and feed it – leading to enormous growth bursts.”

“The team used a new technique called ‘heat-wave mapping’ which uses the growth burst’s own flash of radiation to map the surface of the disk using methanol masers,” Professor Ellingsen said.

Lead researcher, Dr Ross Burns, from the National Astronomical Observatory of Japan (NAOJ) said this research involved the efforts of more than 150 individuals.

“Data from observations from 24 radio telescopes from across the globe contributed to this finding, and those data were carefully correlated by teams at three data centres in three different continents – it’s a huge collaborative effort to advance our knowledge about space,” Dr Burns said.

Four orange spiral arms rotate around a bright yellow centre point.
Artist’s impression of spiral arms within the rotating disk of gas and dust during the formation of a high-mass protostar. Credit: Charles Willmott and Ross Burns.

Dr Burns said this work has been able to confirm the accuracy of some theories that have been hypothesized for over 20 years.

“If more spiral systems and growth bursts are discovered in other high-mass protostars, either using heat-wave mapping or other observational techniques, then astronomers will be able to provide a better understanding of the births of high-mass stars, and therefore a better understanding of our universe.

“This is a very exciting discovery!” he said.

This research was published in Nature Astronomy.

Main image: Map of the 6.7 GHz methanol maser emission in G358-MM1, imaged using heatwave mapping. Spiral structures can be seen, wrapping around the protostar in a clockwise direction. Colours show the velocity of gas and indicate that the system is rotating, in the form of a Keplerian disk, around G358-MM1.