Webb Telescope proves galaxies changed the early universe

The James Webb Space Telescope has returned extremely detailed images and spectra of galaxies that existed when the universe was only 900 million years old. “In the near-infrared Webb image, we can see structures in each galaxy detected by the telescope,” said Jorit Matti from ETH Zurich. “Webb shows us the adventurous youth of these first galaxies.”

These galaxies appear more chaotic than galaxies in the neighboring universe; They are bulky and usually long. These galaxies are also younger and actively forming stars. The stars Webb discovered are increasing in mass, which could lead to large numbers of colorful supernovae in these galaxies.

In the early universe, the gas between stars and galaxies was opaque; energetic starlight could not penetrate it. However, 1 billion years after the Big Bang, the gas became completely transparent. New data from NASA’s James Webb Space Telescope reveals exactly why: Galaxies’ stars emit enough light to heat and ionize the gas around them, clearing our collective view for hundreds of millions of years.

The results, from a team of researchers led by Simon Lilley of ETH Zurich in Switzerland, are the latest insight into a period known as the Epoch of Reionization (see image below), when the universe underwent dramatic changes. After the Big Bang, the gas in the universe was incredibly hot and dense. Over hundreds of millions of years, the gas cooled. Then the universe pressed the button again. The gas heated and ionized again, possibly due to the formation of early stars in the galaxies, and became transparent over millions of years.

13 billion years ago, in the age of reionization, the universe was a very different place. The gas between galaxies was mostly impermeable to energetic light, making it difficult to observe young galaxies. As stars and young galaxies continued to form and evolve, they began to change the gas around them. Over hundreds of millions of years, the gas changed from a neutral, opaque gas to an ionized, transparent gas.
What allowed the universe to become completely ionized, leading to the “open” conditions we see in the universe today?

Researchers have long sought definitive evidence to explain these transformations. The new results effectively pull back the curtain on the end of this reionization period. “Not only does Webb clearly show that these transparent regions exist around galaxies, we also measured their sizes,” explained Daichi Kashino of Nagoya University in Japan, lead author of the team’s first paper. “Thanks to Webb’s data, we can see how galaxies reionize the gas around them.”

These regions of transparent gas are huge compared to galaxies; Imagine a balloon with peas hanging inside. Webb’s data shows that these relatively small galaxies are causing reionization, clearing huge regions of space around them. Over the next hundred million years, these transparent “bubbles” continued to grow larger and larger, eventually merging and the entire universe becoming transparent.

Lilly’s team deliberately targeted a time before the end of the reionization period, when the universe was neither completely pure nor transparent but contained fragments of gas in various states. Scientists pointed Webb in the direction of a quasar, an extremely bright, active, supermassive black hole that acts like a giant flashlight, releasing gas between the quasar and our telescopes. (Look for it in the middle of the image: it’s small and pink, with six prominent diffraction spikes.)

The north and east compass arrows indicate the direction of the image in the sky. Notice that the relationship between north and east in the sky (as seen from below) is opposite to the directional arrows on the world map (as seen from above). The scale is marked with 1 arc minute.
This image shows invisible near-infrared light waves converted into visible light colors. The color key indicates which NIRCam filters were used during light collection. The name color for each filter is the visible light color used to represent infrared light passing through that filter. In this image, blue, green, and red are assigned to NIRCam data at 1.15, 2, and 3.65 microns (F115W, F200W, and F365W), respectively.

As the quasar’s light reached us by passing through various pieces of gas, it was either absorbed by the opaque gas or moved freely in the transparent gas. The team’s breakthrough results came only when Webb’s data were combined with observations of the central quasar at the WM Keck Observatory in Hawaii, as well as the European Southern Observatory’s Very Large Telescope and the Magellan Telescope at Las Campanas Observatory (both in Chile). It became possible.

The researchers then used Webb to identify galaxies near this line of sight and showed that the galaxies were typically surrounded by open areas with a radius of about 2 million light-years. In other words, Webb witnessed galaxies clearing the space around them at the end of the reionization period. To put this into perspective, the space cleared by these galaxies is about the same distance as the distance between our Milky Way galaxy and our nearest neighbor, Andromeda.

Until now, researchers had no definitive evidence of what causes reionization; Until Webb, they weren’t sure exactly what was responsible.

What do these galaxies look like? “They are more chaotic than the neighboring universe,” explained Jorit Matti of ETH Zurich, lead author of the team’s second paper. “Webb shows that they were actively forming stars and must have launched many supernovae. They had quite an adventurous youth!”

Meanwhile, using Webb’s data, Eulers confirmed that the black hole in the quasar at the center of this field was the largest black hole ever known in the early universe, weighing 10 billion times the mass of the Sun. “We still can’t explain how quasars can get so large so early in the history of the universe,” he shared. “That’s another puzzle to solve!” The spectacular images taken by Webb also found no evidence of gravitational lensing of the light from the quasar, making the mass measurements accurate.