First galaxies turned early universe from 'opaque to transparent' after Big Bang, Webb finds

How this drastic transformation occurred is a great puzzle that scientists have been mulling over for decades. 

The JWST’s latest observation 

Webb's superpower to gaze back in time has aided a team of astronomers in finding some definitive evidence. 

The latest observations reveal that early galaxies may have played a part in this dramatic cosmic evolution. These galaxies existed 900 million years after the big bang. Astronomers believe that the stars in some of the early galaxies released enough light to heat and ionize the surrounding gas. This, in turn, began to remove the dense gas fog over hundreds of millions of years. 

“As we look back into the teeth of reionization, we see a very distinct change. Galaxies, which are made up of billions of stars, are ionizing the gas around them, effectively transforming it into transparent gas,” said Simon Lilly, an astronomer at ETH Zürich in Switzerland, in a press release by NASA. 

The observations suggest that space areas around these tiny galaxies formed small transparent "bubbles," which grew larger and larger, eventually merging with one another and rendering the entire universe transparent over the following hundred million years. 

Webb measured that galaxies were generally surrounded by transparent regions about two million light-years in radius. 

Studying the light of the distant quasar 

For this observation, the light source is a luminous quasar J0100+2802, which are bright galactic cores that are considered to be fueled by supermassive black holes.

The scientists concentrated on 59 galaxies using the light of this quasar. Its huge flashlight illuminated the gas between the quasar and the telescopes. The light moved toward us through various regions of cosmic gas, including opaque or transparent gas, along the way. 

“By illuminating gas along our line of sight, the quasar gives us extensive information about the composition and state of the gas,” explained Anna-Christina Eilers of MIT in Cambridge, Massachusetts. 

Surprisingly, this quasar's black hole is the most massive known in the early cosmos, weighing 10 billion times the mass of our Sun. The team highlights that this is another puzzle to solve because they are unsure what caused the black hole to grow so huge in the early universe. 

Along with Webb's observations, multiple ground-based telescopes were put into action — the W. M. Keck Observatory in Hawaii and the European Southern Observatory's Very Large Telescope, and the Magellan Telescope at Las Campanas Observatory in Chile. 

These notable Webb observations have been carried out by multiple research institutes, and the results were reported in three separate papers in the Astrophysical Journal.