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Journalism of Courage
Soon after the birth of the universe, the gas in between stars and galaxies was opaque and starlight could not penetrate it. But a billion years after the big bang, this gas had become completely transparent. The James Webb Space Telescope has helped scientists understand how exactly this happened, according to NASA.
In three new studies published in The Astrophysical Journal, astronomers have put down the latest insights from a period called the epoch of reionisation, a time immediately following the birth of the universe with the big bang, when it underwent dramatic changes.
Immediately after the big bang, the gases in the unvierse were remarkably hot and dense but over a period of hundreds of millions of years, this gas cooled. Then, the universe hit repeat. This gas again became hot and ionised. This is likely due to the formation of early stars in galaxies. This is why the universe became, in a sense, transparent.
Put simply, the stars in the galaxies emitted enough light to heat and “ionise” the gas around them.
According to the space agency, astronomers have been looking for definitive evidence to explain these transformations for a long time. “Not only does Webb clearly show that these transparent regions are found around galaxies, we’ve also measured how large they are. With Webb’s data, we are seeing galaxies reionise the gas around them,” explained Daichi Kashino of Nagoya University in Japan, the lead author of the team’s first paper, in a press statement.
Using Webb, the astronomers are able to observe galaxies that are billions of light-years away. Since light takes billions of years to travel the distance, they are actually observing the galaxies as they were all that time ago.
Those regions of transparent gas are humongous compared to the galaxies. Kashino used the metaphor of a hot air balloon with a pea suspended inside to describe the magnitude in size difference between the galaxies and the regions of gas. But Webb’s data shows that these relatively tiny galaxies drove reionisation and cleared the massive regions of space around them.
