Scientists shed new light on how stars are born

26 Jan 2021

The Milky Way. Image: © Ivan Kurmyshov/

New research from the University of Bath and the Spanish national observatory suggests that star-formation processes could be the same across the universe.

How stars are formed is still one of big mysteries in astrophysics. While we know what stars are made of – mostly hydrogen and helium that produce light and heat – we haven’t yet figured out how exactly these gaseous elements of a galaxy come together.

New findings from teams at the University of Bath and the Spanish national observatory in Madrid may have brought us one step closer. Research published in the Journal of Astronomy and Astrophysics sheds some light on how stars might have formed during the early days of the universe. During this time, star and galaxy formation happened more frequently than it does now.

Prof Carole Mundell, head of astrophysics at the University of Bath and a co-author of the paper, explained the research process. “The little galaxy we’ve been studying was born in a violent, gas-rich galactic collision and offers us a unique laboratory to study the physics of star formation in extreme environments,” she said.

That “little galaxy” is a tidal dwarf galaxy, one that would have formed from the debris after two older galaxies collided with force. These smaller galaxies are commonly used by scientists to learn more about the formation of other ones, such as the Milky Way.

To examine this galaxy, the researchers employed the Atacama Large Millimeter Array (ALMA) in Chile. ALMA made it possible to view even the smallest details of the tidal dwarf galaxy, they said, despite its distance of around 50m light years from Earth.

Using ALMA, they learned that the molecular clouds in a tidal dwarf galaxy are similar in size and content to those in the Milky Way, a much older galaxy thought to be more than 13bn years old. The researchers believe this suggests that the same star-formation process might be occurring all across the universe.

A new question raised for star formation

However, the researchers also noted that the tidal dwarf galaxy – called TDG J1023+1952 – displayed large amounts of dispersed gas. While gas is a common feature of galaxies like the Milky Way, it appears as clouds that act as “star-forming factories”, they said.

“The fact that molecular gas appears in both cloud form and as diffuse gas was a surprise,” Mundell said.

Dr Miguel Querejeta of Spain’s national observatory added: “ALMA’s observations were made with great precision so we can say with confidence that the contribution of diffuse gas is much higher in the tidal dwarf galaxy we studied than typically found in normal galaxies.

“This likely means most of the molecular gas in this tidal dwarf galaxy is not involved in forming stars, which questions popular assumptions about star formation.”

Lisa Ardill was careers editor at Silicon Republic until June 2021