Galaxies may have formed earlier than previously thought, claims new study on first-generation stars
For future studies, scientists are hoping that the James Webb Space Telescope — set to launch in 2021 — will provide answers about first-generation stars
The first stars to ever populate the universe might be older than previously thought, according to researchers hunting for the first generation of stars. These findings could mean that astronomers will have to employ the upcoming James Webb Space Telescope, a successor to Hubble, to peek further into the past. In this study, researchers from NASA and the European Space Agency (ESA) used the Hubble space telescope to hunt for the first formed stars dubbed "Population III" in a variety of galaxies that formed about 500 million to 1 billion years after the big bang. Their analysis found no clues to indicate that the population existed in that period.
"These results have profound astrophysical consequences, as they show that galaxies must have formed much earlier than we thought," the study's lead author Rachana Bhatawdekar, a research fellow at the ESA, said in a statement. The first-generation stars — forged from materials spewing out of the Big Bang — were only made of hydrogen, helium and lithium. These stars and their descendants then created heavy elements, such as oxygen, nitrogen, carbon and iron in their cores, according to researchers.
In their quest to hunt down these stars, Bhatawdekar and her colleagues used the NASA/ESA Hubble Space Telescope, NASA's Spitzer Space Telescope and the European Southern Observatory's Very Large Telescope in Chile. The team used a technique called gravitational lensing, which takes advantage of galaxies located ahead or in the foreground of the target: far-off galaxies.
For this to work, the foreground galaxy has to be large enough to magnify the light coming from distant stars allowing researchers to view them. The team then removed the light from the former to discover galaxies that were not previously observed with the Hubble. In other words, they were able to look at a distance corresponding to when the universe was less than a billion years old.
Their observation of far-off galaxies throws weight on the idea that they were behind a transition phase in the universe called cosmic reionization. During this period, ultraviolet and X-ray radiation, which escaped from the first generations of galaxies, heated up their surrounding, thereby breaking the hydrogen atoms into their constituent protons and electrons. Understanding this phase can help astronomers understand how our universe evolved.
However, it did not indicate they were stars of the period that were the first to populate the galaxy. "We found no evidence of these first-generation Population III stars in this cosmic time interval," Bhatawdekar said. Hubble allows astronomers to view the universe back to within 500 million years of the big bang. So, for future studies, scientists are hoping that the James Webb Space Telescope —set to launch in 2021 — will provide answers about first-generation stars.
These results are based on a paper that will appear in an upcoming issue of the Monthly Notices of the Royal Astronomical Society (MNRAS) and a previous 2019 study by Bhatawdekar and her colleagues. These results are also being presented at a press conference during the 236th meeting of American Astronomical Society.