Astronomers announced Tuesday they have seen through the fog of the early universe to spy some of the first light emitted during a "cosmic renaissance" that occurred when the first galaxies were born.

Researchers say that shortly after the Big Bang, the universe was loaded mostly with hydrogen and helium that was ionized -- too hot to remain in a stable state. For about 300,000 years, the universe expanded and cooled, and the gases began to recombine and stabilize to neutral states.

The universe then entered the dark ages, estimated to have lasted about half a billion years. All the while, clumps of matter developed. Then the first stars, galaxies and quasars formed. Quasars are incredibly bright objects thought to harbor black holes with masses billions of times that of our Sun.

Like morning sunlight burning through fog, the radiation from these new objects made the opaque gas of the universe become transparent by splitting atoms of hydrogen into free electrons and protons, say researchers, who call this period one of re-ionization

"The results are now telling us when this process was completed," said Sir Martin Rees, a cosmologist at Cambridge University who is familiar with the study. Rees told SPACE.com that the results are important for pinning down a time chart of the universe.

"It is as if the universe was filled by a dark, opaque fog up to that time," explains Sandra Castro, a postdoctoral student at Caltech and member of the team. "Then the fires -- the first galaxies -- lit up and burned through the fog. They made both the light and the clarity."

The researchers studied the spectra, or spectrum of light emissions, of a quasar called SDSS 1044-0125, discovered last year by the Sloan team. The spectra of the quasar were obtained at the W. M. Keck Observatory atop Mauna Kea, Hawaii.

In the Keck observations, researchers found not only clear areas of sky but also large, leftover dark regions caused by the opaque gas from the dark ages. Scientists know that certain wavelengths of ultraviolet light are either absorbed or pass through hydrogen depending on its atomic state. In this case, the light emitted by the quasar was absorbed by intervening "neutral" hydrogen -- the non-ionized hydrogen that was the supposed fog of the dark ages. In other patches, some of the hydrogen had apparently been re-ionized, because the ultraviolet light passed through.

They say the conversion from an opaque to transparent universe was not instantaneous. It may have taken tens or even hundreds of millions of years for the earliest quasars and galaxies to burn through the cosmic fog.

The data show the trailing end of this time of change, said Daniel Stern, a scientist at NASA's Jet Propulsion Laboratory who worked on the new study, which been submitted for publication in the Astrophysical Journal Letters.

"There were opaque regions in the universe back then, interspersed with bubbles of light and transparent gas," Stern said. "This is exactly what modern theoretical models predict."

Stern said the beginning of the cosmic renaissance could not be seen because it "seems to be just outside the range of our data." The quasar studied by Stern and his Caltech colleagues was slightly closer than the one studied by the team that found evidence for the dark ages, and it is estimated to have formed a hundred millions years later.

"We had not seen [the re-ionization] before," said Abraham Loeb, a Harvard University astronomer who was not involved in the work but is familiar with it. "This is the first indication that we're getting close to it or perhaps we have seen it."

In a 114-page paper recently published in Physics Reports, Loeb and colleague Rennan Barkana of Princeton University detailed the re-ionization process and predicted that observations were on the threshold of confirming it.

But more observational and theoretical study is now needed to confirm the new results, Loeb said in a telephone interview. "Before we can jump to conclusions we need more examples of these quasars," he said.