Researchers will be able to understand mysterious 're-ionization epoch' in the universe with the help of earliest galaxies. On the basis of data collected by the NASA/ESA Hubble Space Telescope, a team of astronomers has found 252 faint dwarf galaxies within three distant galaxy clusters.

NASA's Hubble space telescope has observed some of the earliest galaxies that were present in the universe some 600 million years after the Big Bang. The energetic electromagnetic radiation, including ultraviolet light released by them reionized the neutral hydrogen atoms, and cleared the fog due to which light could travel to the vast universe corners.

Astronomer Johan Richard of the Observatoire de Lyon, France, said, "The faintest galaxies detected in these Hubble observations are fainter than any other yet uncovered in the deepest Hubble observations". The researchers said that using latest information they have estimated that the universe became completely transparent nearly 700 million years after the Big Bang.

Although the orbital observatory has gone through a number of problems, it has faced them and has overcome the setbacks, emerging as one of the most important astronomical instruments of the world since the small telescope Galileo has stopped working. The functioning of telescope takes place using gravitational lensing that is caused by large galaxy clusters that warp spacetime.

The beginning of Reionization took place when the thick fog of hydrogen gas that cloaked the early universe started clearing.

Since long, scientists were baffled over how the universe pierced the thick veil of hydrogen gas that covered it for millions of years after the Big Bang.