Baby galaxies rotate like mature spirals 

Baby galaxies rotate like mature spirals 

Read time: 3 minutes

ALMA has discovered that young baby galaxies were already very well-behaved. The discovery is a big surprise to astronomers. Everyone believed that newborn galaxies would be very chaotic, with gas moving around in every possible direction. Instead, ALMA found two baby galaxies that already rotated like our own mature Milky Way – in a regular, whirlpool-like way. 

The very first galaxies in the universe formed from collapsing clouds of gas. They were small and dusty, and they had an irregular shape. Many astronomers believed that the gas in such baby galaxies would move in a turbulent way. Renske Smit, a Dutch astronomer working in Cambridge, England, decided to look. 

Renske and her colleagues used ALMA to study two baby galaxies in the early universe. The two galaxies are so far away that their light has taken some 13 billion years to reach us. That means that we see the galaxies as they were in the early days of the universe, just 800 million years after the big bang. 

Thanks to the keen eyesight and the sensitivity of ALMA, it was possible to study the motion of gas clouds inside the two galaxies. The surprising result: they are already very well-behaved, showing a clear whirlpool-like behavior, just like more mature spiral galaxies. 

Renske and her colleagues now plan to study more newborn galaxies, to see if they, too, show evidence of ordered rotation. 


The two galaxies explored by ALMA are so far away that their light took 13 billion years to reach us. Still, ALMA was able to study the millimeter and submillimeter radiation from the two galaxies. The team precisely measured the wavelength of this radiation at different points in the galaxies. The measurements told them that one side of each galaxy is approaching us, while the opposite side is receding. This means that both galaxies rotate in an orderly fashion, like giant whirlpool. 


The research on the two distant galaxies was carried out by an international team of astronomers. The team was led by Renske Smit of the Kavli Institute of Cosmology at the 

University of Cambridge in the United Kingdom. Renske teamed op with some of her former colleagues at Leiden University in the Netherlands, and with astronomers in the United States, Switzerland and Chile. The new results have been published in the weekly magazine Nature. They were also presented at the 231st meeting of the American Astronomical Society in Washington, D.C.