Scientists Discover Leftovers From The Universe's Very First Stars

Astronomers have not yet seen the universe's initial stars, but they are now beginning to discover the ruins of those first stars. Using the Very Large Telescope (VLT) of the European Southern Observatory (ESO), researchers have discovered the fingerprints left by the explosion of the first stars in the cosmos for the first time.

Three far-off gas clouds were discovered, and their chemical make-up matches what scientists anticipate from the earliest star explosions.

"For the first time ever, we were able to identify the chemical traces of the explosions of the first stars in very distant gas clouds," says Andrea Saccardi, a PhD student at the Observatoire de Paris (PSL), who led this study during his master's thesis at the University of Florence.

As per the statement released by the ESO, researchers think that the first stars that formed in the universe were very different from the ones we see today. When they appeared 13.5 billion years ago, they contained just hydrogen and helium, the simplest chemical elements in nature. These stars, thought to be tens or hundreds of times more massive than our sun, quickly died in powerful explosions known as supernovae, enriching the surrounding gas with heavier elements for the first time. Later generations of stars were born out of that enriched gas, which in turn ejected heavier elements as they too died.

But the very first stars are now long gone, so how can researchers learn more about them?

"Primordial stars can be studied indirectly by detecting the chemical elements they dispersed in their environment after their death," says Stefania Salvadori, 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, seen when the universe was just 10-15% of its current age, and with a chemical fingerprint matching what we expect from the explosions of the first stars.

Depending on the mass of these early stars and the energy of their explosions, these first supernovae released different chemical elements such as carbon, oxygen, and magnesium, which are present in the outer layers of stars.