Astronomers find distant gas clouds with remnants of the first stars. Astronomers have yet to see the first stars in the universe, but now they are beginning to find the remains of those first stars. Using the Very Large Telescope (VLT) of the European Southern Observatory (ESO), researchers have discovered for the first time the fingerprints left by the explosion of the first stars in the universe.
Three distant gas clouds were discovered, and their chemical composition matched what scientists expected from early starbursts. “For the first time, we were able to identify the chemical signatures of the first stellar explosions in very distant gas clouds,” says Andrea Zaccardi, a PhD student at the Observatoire de Paris (PSL) who led the study. His master’s thesis at the University of Florence. According to a report published by ESO, researchers believe that the first stars to form in the universe were very different from the stars we see today. When they formed 13.5 billion years ago, they consisted of hydrogen and helium, the simplest chemical elements in nature. These stars, thought to be tens to hundreds of times larger than our Sun, quickly died in powerful explosions called supernovae, enriching the surrounding gas with heavier elements for the first time. Later generations of stars were born from that enriched gas, which also ejected heavier elements as they died. But the first stars are already gone, so how can researchers learn more about them?
“It can be tested indirectly by detecting the chemical elements scattered in their environment after the death of protostars,” says Stefania Salvatori, associate professor at the University of Florence and co-author of the study published today in the Astrophysical Journal. Using data taken with ESO’s VLT in Chile, the team found three very distant gas clouds, the universe only 10-15% of its present age and matching the chemical signature we expect from the explosions of the first stars. Depending on the mass of these early stars and the energy of their explosions, these early supernovae released different chemical elements, such as carbon, oxygen, and magnesium, present in the stars’ outer layers.