spaceSpace and Physics

A Distant, Dusty Galaxy Reveals What The First Stars Got Up To


Dr. Alfredo Carpineti

Senior Staff Writer & Space Correspondent

clockMar 8 2017, 17:30 UTC

Artist impression of A2744_YD4. ESO/M. Kornmesser

The technology to see the first population of stars is not quite there yet, so we have to study them indirectly, looking at the effects they have on the early universe. And the Atacama Large Millimeter/submillimeter Array (ALMA) has stepped up its game to help scientists in this endeavor.

An international team of astronomers, led by Nicolas Laporte from University College London (UCL), used the array to observe A2744_YD4, the most distant object ALMA has ever seen. Its light comes from over 13.2 billion years ago and, while the distance is exciting for record-keeping, the researchers were more surprised to discover that this object was rich in dust.


Dust is formed by stars going supernova and it leads to the formation of small stars like the Sun as well as planets, moons, and even us. The amount of dust in this galaxy is 6 million times the mass of the Sun, an incredibly high amount for a galaxy that has been active for about 200 million years. 

“Not only is A2744_YD4 the most distant galaxy yet observed by ALMA but the detection of so much dust indicates early supernovae must have already polluted this galaxy,” Laporte said in a statement.

The first stars were made exclusively of hydrogen and helium, and as they performed nuclear fusion they formed heavier and heavier elements in their core. When they turned into supernovae they spread those elements that went into making new stars. This study reveals how quickly the first stars in the universe produced the elements we are made of.


As reported in the paper that will appear in the Astrophysical Journal Letters, the team estimated that this galaxy is about 0.2 percent of the mass of the Milky Way and it’s producing stars 20 times faster, with about 20 new Sun-sized stars being born every year.

“This rate is not unusual for such a distant galaxy, but it does shed light on how quickly the dust in A2744_YD4 formed,” added co-author Richard Ellis, from the European Southern Observatory and UCL. “Remarkably, the required time is only about 200 million years – so we are witnessing this galaxy shortly after its formation.”

These observations were possible because the galaxy was lensed by a huge spacetime-bending galaxy cluster. And they have highlighted the incredible capabilities of ALMA to push further back into the mysterious past of the universe. Hopefully, when the James Webb Space Telescope (JWST) goes online in 2018, it will be able to see even further.


A2744_YD4 as seen by ALMA and Hubble Observation of Gravitational Lensing Cluster Abell 2477. ALMA (ESO/NAOJ/NRAO), NASA, ESA, ESO and D. Coe (STScI)/J. Merten (Heidelberg/Bologna) 

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