Many of us would never have thought of the fact that scientists could actually look back in time.
The power of telescopes allows us to study phenomena that occurred billions of years ago, and even glimpse the dawn of creation itself.
Now, astrophysicists have solved a great mystery at the heart of the birth of our universe, when everything was covered by a thick fog.
In four separate papers published in (or accepted in) The Astrophysical Journalscientists at MIT, Japan’s Nagoya University, ETH Zurich and the University of Groningen in the Netherlands have shared some stunning insights into the era known as the Epoch of Reionisation.
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Relatively little is known about this period, when the thick fog that enveloped the universe was gradually lifted, allowing the stars and galaxies to shine.
However, new observations made with the James Webb Space Telescope (JWST) are beginning to undo all of this.
Now, scientists have finally figured out why a billion years after the Big Bang, that thick fog finally dissipated.
First of all, what exactly is the Epoch of Reionisation?
In the first billion years after the Big Bang, the universe was filled with a complex mist of ionized gas that light could not penetrate.
As the gas begins to cool, protons and electrons begin to combine to form mostly neutral hydrogen atoms and some helium.
These clumps of neutral hydrogen are believed to begin forming stars, which coalesce into galaxies.
This process re-ionizes the gas but, since space has expanded at this point, the newly ionised hydrogen is sufficiently diffuse to allow light to flow through, as Science Alertstars.
After a few million years, the universe became the clear galaxy with which we are familiar today.
To explain, here’s a look at what those four new papers revealed about what made space clearer.
In the first study, researchers at the University of Groningen revealed that they discovered important evidence of star formation during the Epoch of Reionisation.
They found a specific wavelength of hydrogen, called hydrogen alpha, which is formed when a star is born and emits large amounts of ionizing ultraviolet radiation.
Until now, no one is sure what produced all the ultraviolet light that appeared during the Epoch of Reionisation.
But, thanks to their discovery of hydrogen alpha, the team of Groningen astronomers that star formation had “a significant role in the reionisation process”.
Another paper, led by Japanese astrophysicist Daichi Kashino, added galaxies to the mix.
According to Kashino and his international team, reionization occurs in “bubbles” around the abundance of newly formed galaxies.
They used JWST data to identify these pockets and precisely measure them, determining that they have a 2 million light-year radius around the small galaxies.
Over the next hundred million years, the bubbles grew and grew, eventually merging and causing the entire universe to become transparent, according to an article published by NASA.
Galaxies have been found to be largely responsible for the “clear” conditions seen in most of the universe todayNASA, ESA, CSA, Joyce Kang (STScI)
A third team of researchers, led by ETH Zurich astrophysicist Jorryt Matthee, analyzed the properties of these bubbles and found that the first galaxies they contained were hot, low in metals and dust and very active.
He said they are “much more chaotic” than those in the nearby universe, adding: “Webb shows that they are actively forming stars and certainly shooting a lot of supernovae. They have a very adventurous youth. !”
The fourth paper, led by MIT cosmologist Anna-Christina Eilers, focuses its attention on the quasar galaxy at the center of the JWST observations.
This quasar is, according to NASA, an “extremely luminous active supermassive black hole that acts like an enormous flashlight”.
Eilers and his team used data from the telescope to confirm that the black hole was the most massive currently known in the early universe, weighing 10 billion times the mass of the Sun.
“We still can’t explain how quasars grew so massive so early in the history of the universe,” he said. “Another puzzle to solve!”
Great if you survived to the end – it’s all pretty heavy. But the main point here is that before JWST no one knew what caused reionization.
Now, thanks to the powerful telescope with the golden eye, one of the great mysteries behind the birth of creation has finally been solved.
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