Universe's Oldest Stars Discovered In An Ancient, Bright Galaxy

Scientists have long believed that the first generation of stars in the universe appeared approximately 800 million years after the Big Bang. These stars -- known as Population III stars -- created by the primordial material from the Big Bang, would have formed out of the only elements that existed at the time -- hydrogen, helium and trace amounts of lithium.

For the longest time, the existence of these massive objects, which were the creators of the first heavy elements that ultimately coalesced into planets and stars we see around us today, has remained purely theoretical -- given the sheer size and age of the universe. However, astronomers now believe they have discovered by far the brightest galaxy yet found in the early universe and strong evidence of the first generation of stars lurking within it.

“The discovery challenged our expectations from the start as we didn’t expect to find such a bright galaxy,” David Sobral from the Institute of Astrophysics and Space Sciences, the Faculty of Sciences of the University of Lisbon in Portugal, who led a team that made the discovery, said in a statement released Wednesday.

The newly found galaxy, named CR7, is three times brighter than the brightest distant galaxy known until now. Based on observations made using the European Southern Observatory's Very Large Telescope (VLT), the astronomers saw signs of strong ionized helium emission and no signs of the heavier elements. This means that there are perhaps no stars with heavy elements in there.

“By unveiling the nature of CR7 piece by piece, we understood that not only had we found by far the most luminous distant galaxy, but also started to realize that it had every single characteristic expected of Population III stars,” Sobral said.

The discovery proves that the much younger Population I and Population II stars were built on the corpses of their ancestors, which had an extremely short lifespan of about 2 million years.

“Those stars were the ones that formed the first heavy atoms that ultimately allowed us to be here,” Sobral said. “It doesn’t really get any more exciting than this.”

Astronomers will now use the VLT, the Atacama Large Millimeter Array and the Hubble Space Telescope to confirm that what has been observed are Population III stars, and to search for more such examples.