Quasar J0100+2802 (NIRCam Image)

There are more than 20,000 galaxies in this field. This NASA/ESA/CSA James Webb Space Telescope view is found between the Pisces and Andromeda constellations.

Researchers using Webb anchored their observations on quasar J0100+2802, an active supermassive black hole that acts like a beacon. It is at the centre of the image above, and appears tiny and pink with six prominent diffraction spikes.

The quasar is so luminous that it acts like a flashlight, illuminating the gas between it and the telescope. The team analyzed 117 galaxies that all existed approximately 900 million years after the big bang – focusing on 59 that lie in front of the quasar. The researchers could study not only the galaxies themselves, but also the illuminated gas surrounding them.

These galaxies existed just before the end of the Era of Reionisation, when the Universe contained a patchwork of gas – some opaque and some transparent (or ionised). 

Researchers have long sought evidence to explain what happened during this period, when the Universe experienced dramatic changes. After the big bang, gas in the Universe was incredibly hot and dense. Over hundreds of millions of years, the gas cooled. Then, the Universe hit “repeat.” The gas again became hot and ionised – and transparent.

The team’s results more concretely define the conditions at this specific “stop” in the Universe’s history. Webb shows that these transparent regions exist around galaxies. They are much like hot air balloons, with galaxies the size of peas clearing that space.

Webb showed that galaxies have fully ionised the gas within a 2 million light-year radius. That’s approximately the same distance as the space between our Milky Way galaxy and our nearest neighbour, Andromeda. Over the next hundred million years, the bubbles went on to grow larger and larger, eventually merging and causing the entire Universe to become transparent.

These results were announced by members of the Emission-line galaxies and Intergalactic Gas in the Epoch of Reionisation (EIGER) team. The team will eventually have images and data from six fields, each centred on a quasar, but Webb’s first image from NIRCam (Near-Infrared Camera) and data known as spectra are so detailed that they could easily make definitive conclusions without waiting for additional observations.

[Image description: Thousands of tiny galaxies appear across the black expanse of space. The galaxy colours vary. Some of the smallest galaxies are shades of orange and pink. Most galaxies are so distant they appear as single points of light. At the centre is a pink object with six diffraction spikes. This is quasar J0100+2802. It appears slightly smaller than the foreground stars, which appear blue.]