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Astronomers find pristine gas from the Big Bang

Astronomers use the light from a quasar to study primordial gas — as it was just moments after the Big Bang.

Astronomers have detected two clumps of primordial gas in deep space — from the dawn of time — using the 10-meter telescopes at the W. M. Keck Observatory. The gas clouds are too diffuse to form stars and show virtually no sign of containing any “metals,” meaning any elements heavier than hydrogen and helium – the two simplest and lightest elements in the universe.

The only elements astronomers have detected in the clouds are hydrogen and its heavier isotope, deuterium. The lack of metals strongly suggests that the gases are reservoirs of pristine material left over from the Big Bang.

Computer simulation of the filamentous region surrounding a galaxy — the place where the two pristine gas clouds could reside. Image Credit: Ceverino, Dekel & Primack

A paper by Astronomer Xavier Prochaska, of the University of California Observatories-Lick Observatory, UC-Santa Cruz, and his team appears online November 20, 2011, at Science Express.

Because stars fuse atoms to make heavier elements, these newly discovered gases have never been involved in any star making in the two billion years between the Big Bang and their discovery. In other words, they are the remnant gases that are unchanged since they were created in the first few minutes after the Big Bang.

Prochaska said:

Despite decades of effort to find anything metal-free in the universe, nature has previously set a limit to enrichment at no less than one-thousandth that found in the sun. These clouds are at least 10 times lower than that limit and are the most pristine gas discovered in our universe.

Another computer simulation showing the filamentous region where pristine gas could reside. Image Credit: Ceverino, Dekel & Primack

Co-author Michele Fumagalli said:

We’ve searched carefully for oxygen, carbon, nitrogen and silicon – the things that are found on Earth and the sun in abundance. We don’t find a trace of anything other than hydrogen and deuterium.

Prochaska explained how they were able to detect dark, cold, diffuse gas about 12 billion light-years away:

In this case we actually have to do a bit of a trick. We study the gas in silhouette.

The light from a more distant quasar shines though the gas. The elements in the gas absorb very specific wavelengths of light, which can only be found by splitting the light into very detailed spectra to reveal the dark lines of missing light.

Fumagalli described it another way:

All of the analysis is on the light we didn’t get. [The clouds absorb only a small fraction of the quasar light that makes it to Earth.] But the signatures of hydrogen absorption are obvious, so there’s no doubt there’s a lot of gas there.

The blobs of pristine gas are good news to astronomers because they are confirmation of the theory of what the first elements were and how they were created in the Big Bang. Hydrogen, helium, lithium and boron are the lightest elements on the periodic table of elements, and they were all created for the first time in what’s called the Big Bang nucleosynthesis (BBN).

Co-author John O’Meara of Saint Michael’s College in Vermont said:

That theory has been very well tested at Keck as regards to hydrogen and its isotope deuterium. One of the conundrums of that previous work, however, is that the gas also showed at least trace amounts of oxygen and carbon. The clouds that we have discovered are the first to match the full predictions of BBN.

The discovery also reveals how different the early universe was from today – where it’s very hard to find any place without some “metals” caused by generations of element-building fusion reactors, aka stars.

Bottom line: Xavier Prochaska, of the University of California Observatories-Lick Observatory, UC-Santa Cruz, and his team have discovered two clumps of primordial gas from the Big Bang, using the 10-meter telescopes at the W. M. Keck Observatory. The gas contains no element heavier than hydrogen and helium, meaning that the gas has never been involved with star formation. Their paper appears online November 20, 2011, at Science Express.

Read more at W. M. Keck Observatory

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