New results from the James Webb Space Telescope show that radiation from ordinary galaxies cleared primordial haze from the Big Bang, allowing the first light to shine through in the early universe. At the beginning of the universe, when the first stars were forming, the space between galaxies was filled with an opaque nebula of neutral hydrogen. But these dark ages did not last long. About 1 billion years after the Big Bang, ultraviolet radiation ionized the space between stars. The universe became transparent and photons could freely circulate in space.

However, the origin of ultraviolet light that caused it to appear reionization period, it was a mystery.

The EIGER project, led by Simon Lilley (ETH Zurich, Switzerland), has published a series of three articles. Astrophysical JournalThey use the near-infrared camera on the James Webb Space Telescope (JWST) along with ground-based observations. The Very Large Telescope for observing SDSS J0100+2802, one of the brightest and most distant quasars from the Magellan and Keck Telescopes.

The gas-sucking supermassive black hole of this quasar produces a bright beam of light that illuminates the gas along the line of sight between us and it. Therefore, astronomers can use the quasar to study the state of gas around interstellar galaxies, particularly distant galaxies that may be associated with reionization.

“We had an excellent complement of the world’s best ground-based telescopes that gave us the spectra of quasars,” says Lilly. period.”

The first study Daichi Kashino (Nagoya University, Japan) reported the discovery of 117 late reionization galaxies in the visible region between us and the quasar. We already knew that during this time period the space between galaxies was partly hazy, partly clear. This work links the galaxies in question to transparent space “bubbles” in which photons can move freely. The further back in time we look at quasars, the smaller the bubbles around galaxies appear.

second study He characterized each of the 117 galaxies in question (again from ETH Zurich), led by Jorrit Matti. All small, young and chaotic, with lots of stars and supernovae. The radiation from all this activity would be enough to ionize the space around the galaxies, allowing the first light to circulate freely.

third study The research, led by Anne-Christina Ehlers (MIT), focused on the quasar itself, the brightest known quasar in the early universe. They checked previous measurements of its mass and determined that it’s probably not gravitational lensing, meaning it’s as bright as it looks. (The immense mass of a quasar at such an early stage of the universe is difficult to explain, but it will forever remain a mystery).

It was already known that in the cosmic milieu of late reionization, there are patches of opaque haze interspersed with ever-growing regions where light can shine freely. But what cleared the transparent bubbles: bright quasars or ordinary galaxies?

Astronomers had suspected for some time that quasars did all the work. But the idea has problems, says George Becker (University of California, Riverside), who was not involved in the research. “This quasar is special because it is extremely bright and at that moment it ionized a very large bubble around it,” he explains. “But by then there aren’t enough quasars to reionize the entire universe.”

“We hypothesized that star-forming galaxies were mainly to blame,” he adds, “but it was unclear whether their ionizing radiation actually reached deep space enough.”

Now astronomers have shown that it is possible. The JWST camera has a mode that lets you capture the spectrum of every galaxy in its field of view. Using this mode, which was originally for calibration purposes, the EIGER team showed that bubbles of transparent ionized gas seen in the quasar’s spectrum are actually related to the exact position of the star-forming galaxies seen by JWST. This supports the idea that ordinary galaxies do most of the work of clearing the space around them.

The EIGER project is currently examining similar data from five other quasars from this early period. And it’s not just them. How Does JWST Re-ionization End Right Now?

“They provide exciting and important insights into three key questions: How did the universe reionize, how did supermassive black holes form in the early universe, and what were the characteristics of the first galaxies. This is great work!”

While JWST has been in operation for just under a year, EIGER and other groups are already well positioned to unravel one of the biggest mysteries in cosmology. And this is just the beginning.