Ancient Gas Cloud May Show Signature Of First Stars In Universe
Scientists from the Swinburne University have hit upon an ancient cloud of gas that might reveal some signature of the first stars that were formed. There are a few heavy elements in the cloud, such as carbon and oxygen, which are less than one-thousandth of that present in the sun. The cloud is situated in a remote region---about billions of light-years away.
"Heavy elements weren't manufactured during the Big Bang, they were made later by stars," said Neil Crighton, lead researcher of the study, in a press release. "The first stars were made from completely pristine gas, and astronomers think they formed quite differently from stars today."
The ancient stars are called Population III stars, and they exploded in a supernovae, which made their heavy elements fly into surrounding clouds of gas. These carry the chemical mark of dead stars.
"Previous gas clouds found by astronomers show a higher enrichment level of heavy elements, so they were probably polluted by more recent generations of stars, obscuring any signature from the first stars," said Crighton.
Hence, the first cloud shows a small percentage of heavy elements, expected for one enriched by ancient stars. Scientists hope to find other such systems that can make clear the ratios of their various elements
"We can measure the ratio of two elements in this cloud, carbon and silicon. But the value of that ratio doesn't conclusively show that it was enriched by the first stars; later enrichment by older generations of stars is also possible," said John O'Meara, co-author of the study. "By finding new clouds where we can detect more elements, we will be able to test for the unique pattern of abundances we expect for enrichment by the first stars."