A 12-billion-year-old gas cloud might be a star graveyard.
The first ever stars, known as Population III (PopIII), are what produced the first heavy elements that are currently found in the universe, and scientists now believe a newly discovered gas cloud may contain their remains. These stars were produced just minutes after the Big Bang about 13.4 billion years ago — a distance that astronomers still cannot see.
Stars were originally divided into two populations by Walter Baade in the 1940s — Population I (PopI) and Population II (PopII). Younger PopI stars are metal-rich, while PopII stars are metal-poor because as stars age they lose their heavier elements to space. However, even these metal-poor stars have concentrations above that of the gas left over from the Big Bang. For this reason, astronomers introduced a third class known as Population III — ancient stars composed entirely of hydrogen and helium.
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This newly discovered cloud contains both hydrogen and helium, but nearly nothing else. According to John O’Meara, co-author of the study, the lack of heavy elements indicates that the gas cloud contains the remains of the universe’s first stars. Scientists want to learn a lot more about these old stars, which have never been observed directly and are still strictly hypothetical, because they are responsible for ejecting carbon, oxygen and other elements into our universe.
Although astronomers are unable to see back to the start of the Big Bang, examining a 12-billion-year-old gas cloud is the next best thing. Their analysis involved measuring the absorption of light of the cloud to determine its composition. What they found was that its composition of heavy metals is about 0.04 percent of that of our sun, and this matches their predictions of the mix of ingredients that would linger around from a star that exploded so long ago.
O’Meara expects that astronomers will find other objects that are similarly lacking in heavy elements, especially once NASA’s James Webb Space Telescope launches in 2018. “This cloud is not a cosmic unicorn,” he said to ScienceNews.
Although we will probably never observe a PopIII star directly, examining their remains could lead to new ideas of how our universe evolved.