Astronomers’ Hopes For Pristine Stars Dashed: They’re Polluted After All
“In 2011, we found the first evidence for unpolluted, pristine gas, but it hadn’t yet collapsed to form stars.
But even bigger news came in 2015, when the galaxy COSMOS Redshift 7 (CR7) was discovered.
From 13 billion years ago, helium lines were observed, without any carbon or oxygen lines.
The hope was that CR7 contained stars made of hydrogen and helium alone.”
In 2015, the galaxy COSMOS Redshift 7 (CR7) was discovered. Its distance is so great that its light is arriving after a 13 billion year journey, meaning it comes from when the Universe was only 6% its current age. Earlier observations, taken with Hubble, showed the presence of hydrogen and helium, but not of heavier elements like carbon, nitrogen or oxygen. Could this be the first example of Population III stars: the first stars made from the pristine material left over from the Big Bang? For years, astronomers thought it just might be, but new observations in the radio from ALMA have crushed those dreams. Looking for the long-wavelength signature of singly-ionized carbon, they’ve found it everywhere, surrounding all the individual, independent components of galaxy CR7.