A “fossilized” cloud of gas that could be from the time of the Big Bang has been discovered by researchers using data from the W. M. Keck Observatory in Hawaii. The distant cloud is one of only three known fossil clouds in the universe, and could provide valuable information about the formation of the earliest galaxies.
The fossil was discovered by examining the spectrum of light given out by a quasar located behind a gas cloud. A quasar emits a bright burst of energy when matter falls into a black hole at the heart of a galaxy, and against the background of this bright light source the shadows of the hydrogen in the gas cloud can be seen. The gas cloud was detected using the Keck Observatory’s Echellette Spectrograph and Imager (ESI) and High-Resolution Echelle Spectrometer (HIRES) instruments which could pick out the shadows of the gas cloud.
The team selected particular quasars to investigate based on previous research where scientists had found shadows from hydrogen but not from heavier elements, suggesting that the gas clouds in question could be from the earliest stages of the universe before heavier elements had formed.
The discovery of this fossil cloud is important because typically when astronomers look at information about the early universe they are working from samples which have been contaminated by later interactions. But the fossil cloud is essentially untouched, giving scientists the opportunity to see the composition of the cloud. “Everywhere we look, the gas in the universe is polluted by waste heavy elements from exploding stars,” PhD student Fred Robert, a member of the research team, explains. “But this particular cloud seems pristine, unpolluted by stars even 1.5 billion years after the Big Bang.”
“If it has any heavy elements at all, it must be less than 1/10,000th of the proportion we see in our Sun,” he went on to say. “This is extremely low; the most compelling explanation is that it’s a true relic of the Big Bang.”
The previous two fossil clouds were discovered by chance, so this marks the first time that a team has searched for and discovered a fossil cloud deliberately.