Sydney, June 21 Scientists in Australia are getting closer to identify the mystery light that lit up the universe.

The universe was covered in a thick fog of neutral hydrogen gas thirteen billion years ago.

However, astronomers have not been able to establish what led the fog to lift, allowing the universe to be lit up.

Dr Emma Ryan-Weber, from Swinburne University in Melbourne, and colleagues hypothesized that the fog cleared when the first stars were formed.

To test that theory, they measured the amount of carbon in the early universe. Because carbon indicates the presence of giant stars, this would show how many stars there were and whether they emitted enough light to clear the fog.

The researchers found that there was not as much carbon as they had expected and therefore massive stars were not solely responsible for the universe's illumination.

"There must have been light coming from something else such as an unknown population of quasars or carbon hidden in unobserved states," The Sydney Morning Herald quoted Ryan-Weber as saying. (ANI)