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| Physics World - How ULAS J1120+0641 may have appeared |
For the first time, astronomers have determined the chemical composition of gas from the first billion years of the universe's life. The gas consists mostly of neutral hydrogen atoms, which means that it may mark the era before stellar radiation began ionizing the universe. Furthermore, the gas shows no signs of the heavy elements that are forged in stars so it may contain only the light elements produced by the Big Bang.
"We are starting to look back to the epoch that is probably when the first stars were turning on," says Robert Simcoe, an astronomer at the Massachusetts Institute of Technology who built the instrument that acquired the spectrum of the far-off gas. "This is the very first [chemical] measurement that anybody has made in any environment at these early times."
The Big Bang, which occurred 13.7 billion years ago, showered the cosmos with hydrogen and helium. Aside from a trace of primordial lithium, heavier elements – which astronomers call metals – arose later, after stars formed and exploded, casting oxygen, iron and other metals into space. Furthermore, the first stars radiated extreme ultraviolet light that ionized gas, tearing electrons from the hydrogen nuclei. The universe is still ionized today.
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"And we who embody the local eyes and ears and thoughts and feelings of the cosmos we've begun, at last, to wonder about our origins. Star stuff, contemplating the stars organized collections of 10 billion-billion-billion atoms contemplating the evolution of matter tracing that long path by which it arrived at consciousness here on the planet Earth and perhaps, throughout the cosmos."
Physics World: Ancient gas sheds light on universe's first billion years
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